Frame construction method, frame construction device and data transfer system capable of accommodating STM traffic and best effort traffic in common frame format

ABSTRACT

A layer 1 network frame is disclosed that includes data of a layer 2 frame. A header of the layer 1 frame header includes: a packet length field to indicate a size of a payload portion of the layer 1 frame, a priority field to indicate a priority of the layer 1 frame, a protocol field to identify a protocol of the data in the layer 2 frame, a frame mode field to indicate a correspondence between the layer 1 frame and the layer 2 frame included within the payload, a stuff field to indicate whether stuff data is contained in the layer 1 frame, and a cyclic redundancy check (CRC) field to indicate a CRC result.

RELATED APPLICATIONS

This application is a Continuation of commonly assigned, co-pending U.S.patent application Ser. No. 09/733,940, filed Dec. 12, 2000, for FRAMECONSTRUCTION METHOD, FRAME CONSTRUCTION DEVICE AND DATA TRANSFER SYSTEMCAPABLE OF ACCOMMODATING STM TRAFFIC AND BEST EFFORT TRAFFIC IN COMMONFRAME FORMAT, the disclosure of which is hereby incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to a frame construction method which canaccommodate STM (Synchronous Transfer Mode), ATM (Asynchronous TransferMode) and IP (Internet Protocol) by use of the same frame format andwhich can transfer a mixture of STM traffic and best effort traffic byuse of the same frame format. The present invention also relates to aframe construction device for constructing such frames and a datatransfer system for transferring such frames.

DESCRIPTION OF RELATED ART

Conventional networks have been constructed mainly in the fields ofcircuit-switched networks (telephone networks (voice transmissiontelecommunication networks), etc.) and networks employing private(leased) lines. However, with the rapid progress of the Internetcommunication of nowadays, data networks, especially networks employingthe IP (Internet Protocol), are growing in high speed. Therefore, theremarkable increase of Internet traffic via modems over voice channelsis putting pressure on the usage status of the circuit-switched networksystems.

The IP data, after being switched (after being connected to an ISP(Internet Service Provider), is transferred in an IP network which iscomposed of leased lines and routers. Meanwhile, transfer capacity ofdata transfer systems in being increased by the speeding-up of SONET(Synchronous Optical NETwork)/SDH (Synchronous Digital Hierarchy) andthe employment of DWDM (Dense Wavelength Division Multiplexing).

Under such complex circumstances of today, networks of various types areconstructed and managed independently, and the construction, managementand maintenance of networks are becoming more and more complicated.

In order to get rid of the complexity, techniques capable ofaccommodating the STM (Synchronous Transfer Mode), ATM (AsynchronousTransfer Mode) and IP (Internet Protocol) in a single packet transfernetwork are becoming necessary.

Such a packet transfer network, in which packet-based data transfer isconducted, is required to transfer STM data of the conventionalsynchronous transfer mode together with ATM data of the asynchronoustransfer mode, and is also required to have the end-to-end circuitquality monitoring functions (end-to-end performance monitoring) whichhave been provided to the conventional networks.

Meanwhile, the packet transfer network is also needed to transferhigh-priority traffic which is required by the next-generation packetcommunication, with the high quality level of the conventional STMsignals.

The next-generation packet communication has to satisfy the aboveconditions, therefore, a frame construction method which can accommodatethe STM, ATM and IP by use of the same frame format is required today,and propositions of data transfer systems based on such a frameconstruction method are sought for.

As a prior art concerning frame construction, the “Simple Data Link”protocol (SDL) has been disclosed in Internet Draft“draft-ietf-pppext-sdl-pol-00.txt”, 1999, Lucent Technologies, IETF(Internet Engineering Task Force).

FIG. 1 is a schematic diagram showing a conventional frame format whichis defined in the prior art (SDL). Referring to FIG. 1, the SDL frameformat includes a header which is composed of two 2-byte fields “PacketLength” and “CRC16”. The “Packet Length” field (identifier) indicatesthe length of the packet (i.e. the payload of the frame), and the“CRC16” field (identifier) indicates the CRC (Cyclic Redundancy Check)result for the “Packet Length” field. The payload of the SDL frame is avariable-length field (0˜64 Kbytes).

A device that received the SDL frame conducts the CRC operation for theheader of the frame and thereby establishes byte synchronization andframe synchronization. By use of the SDL frame format, continuoustransfer of variable-length packets of a single protocol is madepossible.

However, the above conventional SDL frame format can not transfer amixture of signals of various protocols (a mixture of STM, ATM and IP,for example), since the conventional SDL frame format does not havefunctions for implementing periodical data transfer of the STM signalswith fixed intervals nor does have information for designating transferscheduling.

SUMMARY OF THE INVENTION

It is therefore the primary object of the present invention to provide aframe construction method which can accommodate STM, ATM and IP by useof the same frame format and which can transfer a mixture of STM trafficand best effort traffic by use of the same frame format.

Another object of the present invention is to provide a frameconstruction device for constructing frames which can accommodate STM,ATM and IP in the same frame format and which can transfer a mixture ofSTM traffic and best effort traffic in the same frame format.

One aspect is directed to a method of constructing a layer 1 frame. Themethod includes forming a payload for the layer 1 frame that includesdata of a layer 2 frame and forming a layer 1 frame header. The layer 1frame header includes: a packet length field to indicate a size of apayload portion of the layer 1 frame, a priority field to indicate apriority of the layer 1 frame, a protocol field to identify a protocolof the data in the layer 2 frame, a frame mode field to indicate acorrespondence between the layer 1 frame and the layer 2 frame includedwithin the payload, a stuff field to indicate whether stuff data iscontained in the layer 1 frame, and a cyclic redundancy check (CRC)field to indicate a CRC result.

Another aspect is directed to a network device. The network deviceincludes means for receiving one or more of an IP (Internet Protocol)packet, ATM (Asynchronous Transfer Mode) cell, or STM (SynchronousTransfer Mode) signal from another network device. The network devicealso includes means for forming a layer 1 frame that includes thereceived IP packet, ATM cell, or STM signal as payload data within thelayer 1 frame. Further, the network device includes means for forming aheader for the layer 1 frame, the header including: a packet lengthfield to indicate a size of the payload data of the layer 1 frame, apriority field to indicate a priority of the layer 1 frame, a protocolfield to identify whether the means for receiving received an IP packet,ATM cell, or STM signal, a frame mode field to indicate a correspondencebetween the layer 1 frame and the payload data within the layer 1 frame,a stuff field to indicate whether stuff data is contained in the layer 1frame, and a cyclic redundancy check (CRC) field to indicate a CRCresult.

Yet another aspect is directed to a data structure stored in a networkdevice. The data structure comprises a payload field for a layer 1frame, the payload including data for a layer 2 frame. The datastructure further includes a layer 1 frame header including: a packetlength field to indicate a size of a payload portion of the layer 1frame, a priority field to indicate a priority of the layer 1 frame, aprotocol field to identify a protocol of the data for the layer 2 frame,a frame mode field to indicate a correspondence between the layer 1frame and the layer 2 frame included within the payload field, a stufffield to indicate whether stuff data is contained in the layer 1 frame,and a cyclic redundancy check (CRC) field to indicate a CRC result.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention will become moreapparent from the consideration of the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram showing a conventional frame format whichis defined in SDL (Simple Data Link);

FIG. 2 is a schematic diagram showing a basic frame format of a layer 1frame in accordance with an embodiment of the present invention;

FIG. 3 is a schematic diagram showing the correspondence between thebasic layer 1 frame of FIG. 1 and a basic layer 2 frame in accordancewith the embodiment of the present invention;

FIG. 4A is a schematic diagram showing a layer 1 frame in accordancewith the embodiment of the present invention for transferring ATM cells;

FIG. 4B is a schematic diagram showing a layer 1 frame in accordancewith the embodiment of the present invention for transferring an STMsignal;

FIG. 4C is a schematic diagram showing a layer 1 frame in accordancewith the embodiment of the present invention for transferring an IPpacket;

FIG. 5A is a schematic diagram showing the composition of the header ofthe layer 1 frame in accordance with the embodiment of the presentinvention;

FIG. 5B is a table showing an example of codes which are used for a“Frame Mode” identifier of the layer 1 frame header of FIG. 5A;

FIG. 5C is a table showing an example of codes which are used for a“Stuff” identifier of the layer 1 frame header of FIG. 5A;

FIG. 5D is a table showing an example of codes which are used for a“Protocol” identifier of the layer 1 frame header of FIG. 5A;

FIG. 6 is a schematic diagram showing a case where a “Stuffing Length”identifier is added to the layer 1 frame header of FIG. 5A when stuffingis executed;

FIG. 7 is a schematic diagram showing the composition of the layer 1frame when the stuffing is executed;

FIG. 8A is a schematic diagram showing the basic composition of thelayer 1 frame;

FIG. 8B is a schematic diagram showing the composition of a BOM(Beginning Of Message) frame in accordance with the embodiment of thepresent invention;

FIG. 8C is a schematic diagram showing the composition of a COM(Continuation Of Message) frame and an EOM (End Of Message) frame inaccordance with the embodiment of the present invention;

FIG. 9 is a schematic diagram showing an example of partitioning of thelayer 2 frame in accordance with the embodiment of the presentinvention, in which a layer 2 frame is partitioned into segments anddistributing to a BOM frame, two COM frames and an EOM frame;

FIG. 10 is a schematic diagram showing an example of frame-multiplexedlayer 1 frames in accordance with the embodiment of the presentinvention, in which a best effort IP layer 2 frame is partitioned intosegments and distributed to a BOM frame and an EOM frame;

FIG. 11 is a schematic diagram showing an example of frame-multiplexedlayer 1 frames in accordance with the embodiment of the presentinvention, in which a best effort IP layer 2 frame is partitioned intosegments and distributed to a BOM frame, a COM frame and an EOM frame;

FIG. 12 is a schematic diagram showing an example of a network as a datatransfer system in accordance with the embodiment of the presentinvention;

FIG. 13 is a schematic diagram showing the transfer of an IP layer 1frame by use of a route label in accordance with the embodiment of thepresent invention;

FIG. 14 is a schematic diagram showing the transfer of an IP layer 1frame by use of a flow label in accordance with the embodiment of thepresent invention;

FIG. 15 is a block diagram showing an example of the internalcomposition of a transmission section of a edge node of the datatransfer system of FIG. 12;

FIG. 16 is a block diagram showing an example of the internalcomposition of a reception section of the edge node;

FIG. 17 is a block diagram showing an example of the internalcomposition of a core node of the data transfer system of FIG. 12;

FIG. 18 is a block diagram showing an example of the internalcomposition of a reception section of the core node;

FIG. 19 is a block diagram showing an example of the internalcomposition of a transmission section of the core node;

FIG. 20 is a schematic diagram showing link monitoring and pathmonitoring which are conducted in the embodiment of the presentinvention;

FIG. 21 is a flow chart showing an algorithm in accordance with theembodiment of the present invention for the transmission of best effortIP layer 1 frames;

FIG. 22A is a schematic diagram showing the composition of a dummy framewhich is employed in the embodiment of the present invention;

FIG. 22B is a schematic diagram showing the composition of a minimaldummy frame which is employed in the embodiment of the presentinvention; and

FIG. 22C is a schematic diagram showing the composition of an OAM(Operating And Management) frame which is employed in the embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, a description will be given in detail ofpreferred embodiments in accordance with the present invention.

The frame in accordance with an embodiment of the present invention,which is designed to accommodate STM (Synchronous Transfer Mode)signals, ATM (Asynchronous Transfer Mode) cells and IP packets in thesame frame format, is implemented by a layer 1 frame and a layer 2 framewhich is contained in the layer 1 frame. The layer 1 frame is avariable-length frame which enables variable-length packet transfer.

The header of the layer 1 frame includes a “Packet Length” identifier, a“Priority” identifier, a “Protocol” identifier, a “Frame Mode”identifier, a “Stuff” identifier and a “Header CRC16” identifier asshown in FIG. 5A. The “Packet Length” identifier indicates the length ofa packet (the payload of the layer 1 frame). The “Priority” identifierindicates the priority of the packet. The “Protocol” identifierindicates a layer 2 protocol (STM, ATM, IP, etc.). The “Frame Mode”identifier indicates the type of the layer 1 frame, that is, thecorrespondence between the layer 1 frame and the layer 2 frame containedtherein. The “Stuff” identifier indicates whether stuff data (data forstuffing) is included in the layer 1 frame or not. The “Header CRC16”identifier indicates the result of 16-bit CRC (Cyclic Redundancy Check)operation for the previous fields (the “Packet Length” identifier, the“Priority” identifier, the “Protocol” identifier, the “Frame Mode”identifier and the “Stuff” identifier).

When the stuffing is not executed, the layer 1 frame includes a“Payload” field (hereafter, referred to as a “layer 1 frame payload” ora “payload”) just after the header as shown in FIG. 8A. The layer 1frame payload is a variable-length field (0˜64 Kbytes). After the“payload, the layer 1 frame includes a “Payload CRC” field whichindicates the result of CRC operation for the layer 1 frame payload.

Also when the stuffing is executed, the layer 1 frame includes a payloadafter the header as shown in FIG. 7. The layer 1 frame payload is avariable-length field (0˜64 Kbytes). In this case, a “Stuffing Length”identifier for indicating the length of the stuff data is provided tothe top of the layer 1 frame payload. The stuff data is inserted at theend of the layer 1 frame payload. The stuff data is data for adjustingthe length of the layer 1 frame. The length of the stuff data isdescribed in the “Stuffing Length” identifier at the transmitting end.After the payload, the layer 1 frame includes a “Payload CRC” fieldwhich indicates the result of CRC operation for the layer 1 framepayload.

The “Header CRC16” identifier of the layer 1 frame header enables adevice that receives the layer 1 frame to establish bit synchronization,byte synchronization and frame synchronization. The “Payload CRC” fieldis used for monitoring payload data quality. Therefore, the layer 1frame enables a device at the receiving end to conduct bitsynchronization, byte synchronization, frame synchronization and payloaddata quality monitoring. In short, the layer 1 frame according to thepresent invention can implement the basic functions of the conventionallayer 1.

The aforementioned layer 2 frame of this embodiment is packed in thepayload of the layer 1 frame. The layer 2 frame can accommodate andtransfer multi-protocol data (STM signals, ATM cells, IP packets, etc.).The protocol of the data contained in the layer 2 frame is indicated bythe “Protocol” identifier of the layer 1 frame header.

The above multiprotocol includes ATM, STM, IPv4 (Internet Protocolversion 4), IPv6 (Internet Protocol version 6), MPLS (MultiProtocolLabel Switching), etc.

The header of the layer 2 frame is placed at the top of the layer 1frame payload. Incidentally, in the case where the stuffing is executed(that is, in the case where the “Stuffing Length” identifier is placedat the top of the layer 1 frame payload), the layer 2 frame header isplaced after the “Stuffing Length” identifier. The length of the layer 2frame header can be changed depending on the protocol of the data whichis contained and transferred in the layer 2 frame.

Here, we define two types of labels as the header of the layer 2 framein the case where an IP packet is transferred in the layer 1 frame: aroute label and a flow label. The route label is a field to be referredto in the routing through nodes of a network. The flow label is a fieldto be used for selecting one OCH (Optical CHannel) (defined by atransmission line and a wavelength) to be used when there are two ormore OCHs between two nodes. Further, as a special-purpose layer 1 framefor monitoring a path between the ingress point and the egress point ofa network, an OAM (Operating And Management) frame is defined.

In cases where an STM signal or ATM cells are transferred in the layer 1frame, the route label can be used for the label information in thelayer 2 frame header for the routing of the layer 1 frame. In thesecases, the flow label is not used, since the amounts of STM traffic andATM traffic are smaller than that of IP traffic and the transfer of thelayer 1 frames for STM and ATM can be conducted by use of a presetwavelength between nodes.

In the following, an explanation will be given on the segmentation ofthe layer 2 frame. The following explanation will be given assuming thatthe layer 2 frame is required to transfer CBR (Constant Bit Rate)traffic such as STM signals. Incidentally, in ordinary data transfer,one layer 2 frame corresponds to one layer 1 frame.

In ordinary packet-based data transfer such as POS (Packet Over Sonet,RFC2615 [Internet Engineering Task Force]), frames containing CBRtraffic have to be transferred with a constant cycle (125 μsec).

However, the transfer of a CBR traffic frame is generally suspendeduntil the transfer of a pervious layer 2 frame (a layer 2 framecontaining best effort traffic etc.) is finished. Therefore, the STMsignals can not be transferred with a constant cycle in ordinarypacket-based data transfer, since each packet is a variable-lengthpacket.

In order to avoid such a problem, in the frame construction method ofthis embodiment, a long layer 2 frame of a low priority is partitionedinto segments and distributed to two or more layer 1 frames.

A high priority layer 1 frame (such as the CBR traffic) is forciblytransferred by means of interruption even if a low priority layer 2frames are being transferred.

The layer 1 frames containing the partitioned layer 2 frames can beclassified into three types: BOM (Beginning Of Message) frames, COM(Continuation Of Message) frames and EOM (End Of Message) frames. TheBOM frame is a layer 1 frame containing the front end of a layer 2frame. The EOM frame is a layer 1 frame containing the rear end of alayer 2 frame. The COM frame is a layer 1 frame which contains apartitioned segment of a layer 2 frame but does not contain the frontend not rear end of the layer 2 frame. In short, a low priority layer 2frame (from its front end to rear end) is partitioned into segments anddistributed to a BOM frame, one or more (or zero) COM frames and an EOMframe.

Whether a layer 1 frame is a frame including the partitioned segments ofa layer 2 frame (BOM frame, COM frame or EOM frame) or not (singleframe) can be judged by referring to the “Frame Mode” identifier whichis included in the layer 1 frame header.

A device that terminates the layer 1 frames refers to the “Priority”identifiers and the “Protocol” identifier in the headers of the layer 1frames and thereby extracts layer 1 frames having the same “Priority”identifier and “Protocol” identifier. By such operation, a BOM frame,COM frames and an EOM frame containing segments of a partitioned layer 2frame are received and transferred successively, thereby the originallayer 2 frame can be reconstructed (recombined and restored) easily.

In the frame construction method of this embodiment, there are caseswhere the layer 2 frame header of a layer 1 frame is omitted. When alayer 2 frame is partitioned into segments and distributed to a BOMframe, COM frames and an EOM frame, header information to be held by theCOM frames and the EOM frame is the same as that of the BOM frame.Therefore, omission of the layer 2 frame header information is allowedin the COM frames and the EOM frame of this embodiment. In other words,the BOM frame contains the layer 2 frame header, however, the COM framesand the EOM frame are not provided with the layer 2 frame headers. Thus,the BOM frame is called an “uncompressed frame”, whereas the COM framesand the EOM frame are called “compressed frames”.

In the following, an explanation will be given on data transfer by useof aggregate frames in accordance with the embodiment of the presentinvention.

The layer 2 frame of this embodiment is capable of accommodating andtransferring two or more data units when transferring data of anupper-layer protocol (STM, ATM, IP, MPLS, etc.)

For example, the STM signals are transferred in units of N bytes (not inunits of bytes). By assigning each byte to a 64 Kbps channel, anN-channel trunk signal of N×64 Kbps is transferred between twoconventional switches.

In this case, a network edge device (such as an edge node) forgenerating the layer 2 frames collects STM data in units of 125 μsec andpacks them in the layer 2 frames. Similarly, for transmitting ATMsignals, the network edge device packs a plurality of ATM cells in alayer 2 frame and transmits the layer 2 frame.

In the following, periodical STM signal transfer (at fixed intervals of125 μsec) which is conducted in this embodiment will be explained.

When layer 1 frames containing STM signals (hereafter, also referred toas “STM layer 1 frames”) have to be transferred at fixed intervals, thelength of a layer 1 frame which is transferred before the STM layer 1frame becomes important.

For instance, even when there are no layer 1 frames to be transferredbefore the STM layer 1 frame, bit synchronization, byte synchronizationand frame synchronization which are implemented by the layer 1 frameshas to be maintained. In such cases, a dummy frame is transferred beforethe STM layer 1 frame and thereby an idle transfer space between the STMlayer 1 frames are filled up.

Whether a layer 1 frame is a dummy frame or not can be judged byreferring to the “Protocol” identifier of the layer 1 frame header. Thedummy frame is a variable-length frame.

When the idle transfer space before the transfer of an STM layer 1 frameis shorter than a shortest dummy frame (minimal dummy frame), theaforementioned stuff data is inserted in a layer 1 frame that istransferred before the idle transfer space, thereby the idle transferspace is filled up and the layer 1 frames become continuous.

The length of the stuff data is shorter than that of the minimal dummyframe. The minimal dummy frame is composed of the layer 1 frame headerand the “Payload CRC” field, therefore, the stuff data length is shorterthan the length of the layer 1 frame header and the length of the“Payload CRC” field added together. Concretely, the stuff data lengthbecomes several bytes.

By the insertion of the dummy frames and the stuff data, the continuoustransfer of the layer 1 frames are realized, the frame synchronizationcan be maintained, and the periodical transfer of the STM layer 1 framesat precisely fixed intervals (125 μsec) is made possible.

FIG. 2 is a schematic diagram showing the basic frame format of thelayer 1 frame in accordance with the embodiment of the presentinvention. As shown in FIG. 2, the layer 1 frame includes the layer 1frame header (6 byte) and the layer 1 frame payload (0-64 Kbytes). The“Payload CRC” field, indicating the result of CRC16 or CRC32 operationfor the layer 1 frame payload, is added optionally.

FIG. 3 is a schematic diagram showing the correspondence between thebasic layer 1 frame and a basic layer 2 frame. Referring to FIG. 3, thelayer 2 frame is composed of a layer 2 header (L2 header) and a datasection. As shown in FIG. 3, the layer 2 frame corresponds to thepayload (0˜64 Kbytes) of the layer 1 frame.

FIGS. 4A through 4C are schematic diagrams showing frames in accordancewith the embodiment of the present invention when ATM cells, STM signalsand IP packets are packed in the layer 2 frames.

In the payload of the layer 1 frame which is shown in FIG. 4A, a layer 2frame, including a header (L2 header) and a plurality of ATM cellshaving the same VPI (Virtual Path Identifier), is packed.

In the payload of the layer 1 frame which is shown in FIG. 4B, a layer 2frame, including a header (L2 header) and STM signals (N×64 Kbps voicedata addressed to the same destination) is packed.

In the payload of the layer 1 frame which is shown in FIG. 4C, a layer 2frame, including a header (L2 header) and an IP packet, is packed.

FIG. 5A is a schematic diagram showing the composition of the header ofthe layer 1 frame in accordance with the embodiment of the presentinvention. As shown in FIG. 5A, the layer 1 frame header (L1 header)includes the “Packet Length” identifier, the “Priority” identifier, the“Protocol” identifier, the “Frame Mode” identifier, the “Stuff”identifier and the “Header CRC16” identifier. In the case where thestuff data is inserted in the layer 1 frame payload, the “StuffingLength” identifier indicating the length of the stuff data is added tothe layer 1 frame header.

The “Packet Length” identifier indicates the length of the payload ofthe layer 1 frame. The “Priority” identifier indicates the priority ofthe layer 1 frame. The “Protocol” identifier indicates a protocol of thedata contained in the layer 2 frame. The “Frame Mode” identifierindicates a method for packing a layer 2 frame in one or more layer 1frames, that is, whether the layer 1 frame is a single frame, a BOMframe, a COM frame or an EOM frame. The “Stuff” identifier indicateswhether the stuff data exists in the layer 1 frame or not. The “HeaderCRC16” identifier indicates the result of 16-bit CRC (Cyclic RedundancyCheck) operation for the above fields (identifiers). The “StuffingLength” identifier indicates the length of the stuff data.

FIG. 5B is a table showing an example of codes which are used for the“Frame Mode” identifier. Referring to FIG. 5B, the “Frame Mode”identifiers (codes) “00”, “01”, “10” and “11” denote a single frame, aBOM frame, a COM frame and an EOM frame, respectively.

FIG. 5C is a table showing an example of codes which are used for the“Stuff” identifier. Referring to FIG. 5C, the “Stuff” identifier (code)“0” indicates that the stuffing is not executed, and the “Stuff”identifier (code) “1” indicates that the stuffing is executed.

FIG. 5D is a table showing an example of codes which are used for the“Protocol” identifier. Referring to FIG. 5D, the “Protocol” identifiers(code) “000”, “001”, “010”, “011”, “100”, “101” denote IPv4, IPv6, STM,ATM, OAM, and a dummy frame, respectively.

As shown in FIGS. 6 and 7, the “Stuffing Length” identifier is added tothe layer 1 frame header when the stuffing is executed and the stuffdata is inserted in the bottom of the layer 1 frame payload.

In the following, a data transfer method for transferring the layer 1frames of this embodiment will be explained. When layer 1 framescontaining STM signals (STM layer 1 frames) and layer 1 framescontaining ATM cells (hereafter, referred to as “ATM layer 1 frames”)are transferred, the STM layer 1 frames and the ATM layer 1 frames aretransmitted periodically. Layer 1 frames containing IP packets(hereafter, referred to as “IP layer 1 frames”) are accommodated inremaining spaces between the STM layer 1 frames and the ATM layer 1frames.

In this embodiment, there are two priority levels with regard to the IPpackets: a primary IP packet and a best effort IP packet. The primary IPpacket is an IP packet whose bandwidth has to be guaranteed or whosedelay is required to be short (delay-sensitive). The primary IP packetis transferred with higher priority than the best effort IP packet.

Therefore, the STM layer 1 frames and the ATM layer 1 frames aretransmitted at predetermined periods, and the layer 1 frames containingthe primary IP packets (hereafter, referred to as “primary IP layer 1frames”) and the layer 1 frames containing the best effort IP packets(hereafter, referred to as “best effort IP layer 1 frames”) aresuccessively transmitted in between the STM layer 1 frames and the ATMlayer 1 frames.

When the transmission of a variable-length best effort IP packet(contained in a best effort IP layer 2 frame in a best effort IP layer 1frame) overlapped with the periodical transmission of the STM/ATM layer2 frames (contained in the STM/ATM layer 1 frames), the best effort IPlayer 2 frame is partitioned into segments and distributed to two ormore best effort IP layer 1 frames. The best effort IP layer 1 framescontaining the partitioned segments of a best effort IP layer 2 frameinclude a BOM frame, COM frames and an EOM frame, as mentioned before.

FIG. 10 is a schematic diagram showing an example of frame-multiplexedlayer 1 frames in accordance with the embodiment, in which a best effortIP layer 2 frame is partitioned into segments and distributed to a BOMframe and an EOM frame. Referring to FIG. 10, a best effort IP layer 2frame is partitioned into two segments and distributed to a BOM(Beginning Of Message) frame (a layer 1 frame containing the front endof the layer 2 frame) and an EOM (End Of Message) frame (a layer 1 framecontaining the rear end of the layer 2 frame).

FIG. 11 is a schematic diagram showing an example of frame-multiplexedlayer 1 frames in accordance with the embodiment, in which a best effortIP layer 2 frame is partitioned into segments and distributed to a BOMframe, a COM frame and an EOM frame. Referring to FIG. 11, a best effortIP layer 2 frame is partitioned into three segments and distributed to aBOM frame, a COM (Continuation Of Message) frame (a layer 1 framecontaining a partitioned segment of a layer 2 frame but not containingthe front end or rear end of the layer 2 frame) and an EOM (End OfMessage) frame. As shown in FIG. 9, the number of COM frames between aBOM frame and an EOM frame is not limited to one. Two or more COM framescan be generated between the BOM frame and the EOM frame depending onthe length of the best effort IP layer 2 frame. When the layer 2 frameto be partitioned is short, no COM frames are generated between the BOMframe and the EOM frame, as shown in FIG. 10.

Referring to FIGS. 10 and 11, if layer 1 frames having the same“Priority” identifier and “Protocol” identifier are extracted, the BOMframe, the COM frames and the EOM frame containing the partitionedsegments of a layer 2 frame are received and transferred in sequence.

A device receiving and terminating the layer 1 frames can discriminatebetween a BOM frame, a COM frame, an EOM frame and a single frame byreferring to the “Frame Mode” identifier which is included in the headerof the layer 1 frame (see FIG. 5B).

If the “Frame Mode” identifier is “00” (single frame), a best effort IPpacket has been packed in the layer 1 frame without being partitioned.

If the “Frame Mode” identifier is “01” (BOM frame), a best effort IPpacket has been partitioned into two or more segments, and the layer 1frame contains the first segment (front end) of the best effort IPpacket.

If the “Frame Mode” identifier is “10” (COM frame), a best effort IPpacket has been partitioned into two or more segments, and the layer 1frame contains a segment of the best effort IP packet that is not thefirst segment not the last segment.

If the “Frame Mode” identifier is “11” (EOM frame), a best effort IPpacket has been partitioned into two or more segments, and the layer 1frame contains the last segment (rear end) of the best effort IP packet.

The BOM frame, the COM frames and the EOM frame are transferredsuccessively and a device at the receiving end extracts layer 1 frameshaving the same “Priority” identifier and “Protocol” identifier,therefore, when the device received a COM frame or an EOM frame (“FrameMode” identifier: “10” or “11”), the device can judge that the COM/EOMframe can be used together with a previously received BOM frame forreconstructing a layer 2 frame.

Therefore, in this embodiment, the layer 2 frame contained in a COMframe or an EOM frame is not provided with a layer 2 frame header. Bythe omission of the layer 2 frame header in the COM/EOM frames, thepayloads of the layer 2 frames can be made longer in the COM/EOM frames,thereby the amount of transferred information can be increased.

The frame format of the layer 1 frame will be explained in detailreferring to FIGS. 8A through 8C. FIG. 8A is a schematic diagram showingthe basic composition of the layer 1 frame of this embodiment. Referringto FIG. 8A, the header of the layer 1 frame includes the “Packet Length”identifier, the “Priority” identifier, the “Protocol” identifier, the“Frame Mode” identifier (unshown in FIG. 8A), the “Stuff” identifier(unshown in FIG. 8A) and the “Header CRC16” identifier. The payload ofthe layer 1 frame is placed in a variable-length field (0˜64 Kbytes)after the header. After the payload, a “Payload CRC16” field or a“Payload CRC32” field is added as an option.

FIG. 8B is a schematic diagram showing the composition of the BOM frameof this embodiment. In the BOM frame as an uncompressed frame, the layer2 frame header (the route label and the flow label) and the layer 2frame payload (data area) are packed in the layer 1 frame payload.

FIG. 8C is a schematic diagram showing the composition of the COM/EOMframe of this embodiment. In the COM/EOM frame as a compressed frame,only the layer 2 frame payload (data area) are packed in the layer 1frame payload. The layer 2 frame header (the route label and the flowlabel) are omitted.

In this embodiment, the layer 1 frames containing STM signals (STM layer1 frames) are transferred at fixed intervals (125 μsec) as shown inFIGS. 10 and 11. A switching section of a node (which relays the layer 1frames) transmits the STM signals (STM layer 1 frames) as traffic of thehighest priority.

For the implementation of the periodical transmission of the STM layer 1frames, a layer 1 frame containing a best effort IP packet (best effortIP layer 1 frame) has to be partitioned into a BOM frame, COM frames andan EOM frame when the transmission of the best effort IP layer 1 frameoverlaps with the transmission of an STM layer 1 frame. Incidentally, aBOM/COM/EOM frame which will be used in the following explanation is abest effort IP layer 1 frame. The STM layer 1 frame, the ATM layer 1frame and the primary IP layer 1 frame are not partitioned andtransferred as single frames.

However, the periodical transmission of the STM layer 1 frames can notbe realized only by the partitioning of the best effort IP layer 1 frameand the high priority transmission of the STM layer 1 frames.

As shown in FIGS. 10 and 11, the STM layer 1 frames are transferred withthe highest priority at fixed intervals (125 μsec), and layer 1 framescontaining ATM cells (ATM layer 1 frames) and layer 1 frames containingprimary IP packets (primary IP layer 1 frames) are also transferred withhigh priority. Therefore, the best effort IP layer 1 frames have to betransferred in transfer spaces (idle time) between the STM layer 1frames, the ATM layer 1 frames and the primary IP layer 1 frames.

The length L of the transfer space (idle time) in which the best effortIP layer 1 frame can be transferred (hereafter, referred to as a “besteffort IP transfer space”) changes depending on the lengths of the ATMlayer 1 frames and the primary IP layer 1 frames. The transfer of theSTM layer 1 frames has to be conducted at predetermined periods asmentioned above. Therefore, the length of the best effort IP layer 1frame has to be adjusted to the length L of the best effort IP transferspace.

In the following, an operation of a device at the transmitting end forfilling up the best effort IP transfer space (to the length: L) by useof a dummy frame or stuff data will be explained referring to FIGS. 7,21, 22A and 22B.

The aforementioned dummy frame is a layer 1 frame whose payload isfilled with null data as shown in FIG. 22A. A dummy frame whose nullarea is 0 Kbyte is the aforementioned “minimal dummy frame”. The minimaldummy frame is composed of the layer 1 frame header and the “PayloadCRC” field only, as shown in FIG. 22B.

The stuff data is data which is inserted into the best effort IP layer 1frame payload for adjusting the length of the best effort IP layer 1frame to the length L of the best effort IP transfer space (see FIG. 7).As shown in FIG. 7, the stuff data is added after the data area of thepayload of the best effort IP layer 1 frame. In the case where the stuffdata is added to the best effort IP layer 1 frame payload, the “StuffingLength” identifier is provided to the top of the payload. In this case,code “1” is described in the “Stuff” identifier of the header as shownin FIGS. 5C and 7.

FIG. 21 is a flow chart showing an algorithm in accordance with thisembodiment for the transmission of the best effort IP layer 1 frames.Incidentally, the following explanation will be given ignoring the“Payload CRC” field for the sake of simplicity.

When a device at the transmitting end (hereafter, referred to as a“frame transmission device”) received a best effort IP layer 1 frametransmission instruction and a parameter L indicating the length L ofthe best effort IP transfer space, the frame transmission device firstjudges whether or not a remaining EOM frame exists (step S2200). If aremaining EOM frame exists (“Yes” in the step S2200), the length M ofthe EOM frame is compared with the length L of the best effort IPtransfer space (step S2201).

If the EOM frame length M is longer than the best effort IP transferspace length L (“M>L” in the step S2201), the EOM frame is partitionedand the first segment of the EOM frame is extracted. The length of theextracted first segment (including a header) is set to L. The extractedfirst segment of the EOM frame is transmitted as a COM frame, and theremaining segment of the EOM frame is stored as an EOM frame (having alayer 1 frame header) (step S2202), thereby the process is ended.

If the EOM frame length M is equal to the best effort IP transfer spacelength L (“M=L” in the step S2201), the EOM frame is transmitted withoutbeing partitioned (step S2203), thereby the process is ended.

If the EOM frame length M is shorter than the best effort IP transferspace length L (“M<L” in the step S2201), the EOM frame length M and theminimal dummy frame length D added together (M+D) is compared with thebest effort IP transfer space length L (step S2204).

If the length M+D is equal to the best effort IP transfer space length L(“M+D=L” in the step S2204), the EOM frame of the length M istransmitted (step S2207) and thereafter the minimal dummy frame of thelength D is transmitted (step S2208), thereby the process is ended.

If the length M+D is longer than the best effort IP transfer spacelength L (“M+D>L” in the step S2204), the stuff data is inserted afterthe payload of the EOM frame. The length of the stuff data is set toL−M−1 bytes. Incidentally, the 1 byte is used for the “Stuffing Length”identifier which indicates the length of the stuff data. Therefore, inthe EOM frame to be transmitted, the “Stuffing Length” identifier (1byte) is inserted at the top of the layer 1 frame payload and the stuffdata (L−M−1 bytes) is inserted at the bottom of the layer 1 framepayload as shown in FIG. 7 (step S2205). Thereafter, the EOM frame istransmitted (step S2206), and thereby the process is ended.

If the length M+D is shorter than the best effort IP transfer spacelength L (“M+D<L” in the step S2204), the EOM frame is transmitted andthe value of the parameter L (best effort IP transfer space length L) isupdated into L−M (L−M→L) (step S2209).

If no remaining EOM frame exists (“No” in the step S2200) or if theupdate of the best effort IP transfer space length L has been conducted(step S2209), the frame transmission device judges whether a best effortIP layer 1 frame to be transferred next exists or not (step S2210).

If no best effort IP layer 1 frame to be transmitted next exists (“No”in the step S2210), a dummy frame of the length L is transmitted so asto implement the periodical transmission of the STM layer 1 frames (stepS2211), thereby the process is ended.

If a best effort IP layer 1 frame to be transmitted next exists (“Yes”in the step S2210), the frame transmission device obtains the length Bof the best effort IP layer 1 frame to be transmitted next (step S2212).

Subsequently, the best effort IP layer 1 frame length B is compared withthe best effort IP transfer space length L (step S2213).

If the best effort IP layer 1 frame length B is longer than the besteffort IP transfer space length L (“B>L” in the step S2213), the besteffort IP layer 1 frame is partitioned into a BOM frame of the length Land an EOM frame (step S2214). Thereafter, the BOM frame of the length Lis transmitted and the EOM frame (having a layer 1 frame header) isstored (step S2215), thereby the process is ended.

If the best effort IP layer 1 frame length B is equal to the best effortIP transfer space length L (“B=L” in the step S2213), the best effort IPlayer 1 frame is transmitted as a single frame without being partitioned(step S2216), thereby the process is ended.

If the best effort IP layer 1 frame length B is shorter than the besteffort IP transfer space length L (“B<L” in the step S2213), the besteffort IP layer 1 frame length B and the minimal dummy frame length Dadded together (B+D) is compared with the best effort IP transfer spacelength L (step S2217).

If the length B+D is equal to the best effort IP transfer space length L(“B+D=L” in the step S2217), the best effort IP layer 1 frame of thelength B is transmitted as a single frame (step S2219) and thereafterthe minimal dummy frame of the length D is transmitted (step S2220),thereby the process is ended.

If the length B+D is longer than the best effort IP transfer spacelength L (“B+D>L” in the step S2217), the stuff data is inserted afterthe payload of the best effort IP layer 1 frame to be transmitted next.The length of the stuff data is set to L−B−1 bytes. The 1 byte is usedfor the “Stuffing Length” identifier indicating the length of the stuffdata. Therefore, in the best effort IP layer 1 frame to be transmittednext, the “Stuffing Length” identifier (1 byte) is inserted at the topof the layer 1 frame payload and the stuff data (L−B−1 bytes) isinserted at the bottom of the layer 1 frame payload as shown in FIG. 7(step S2221). Thereafter, the best effort IP layer 1 frame istransmitted as a single frame (step S2222), and thereby the process isended.

If the length B+D is shorter than the best effort IP transfer spacelength L (“B+D<L” in the step S2217), the best effort IP layer 1 frameis transmitted as a single frame and the value of the parameter L (besteffort IP transfer space length L) is updated into L−B (L−B→L) (stepS2218). Thereafter, the process is returned to the step S2212.

By the processes which has been described above, the best effort IPtransfer space of the length L is precisely filled up and thereby theperiodical transmission of the STM layer 1 frames is realizedsuccessfully. Therefore, the STM signals can be transferred end-to-endthrough the packet-based network.

In the following, an explanation will be given on the layer 2 frameheader in accordance with this embodiment referring to FIGS. 4C, 8B, 13and 14.

In the case where an IP packet is transferred in a layer 2 frame, thelayer 2 frame is provided with the aforementioned layer 2 frame headerwhich is composed of the route label and the flow label, as shown inFIG. 4C.

The route label is a field which is referred to for the routing throughnodes of the network. The flow label is a field which is used fordesignating one OCH (Optical CHannel) (transmission line and wavelength)to be used when there are two or more OCHs between two nodes.

As mentioned before, in the case of the best effort IP layer 1 frames,the route label and the flow label as the layer 2 frame header are addedto the BOM frames only as shown in FIG. 8B, and are not added to the COMframes and the EOM frames as shown in FIG. 8C. FIGS. 13 and 14 show thetransfer of IP layer 1 frames by use of the route label and the flowlabel. Details of frame transfer process using the route label and theflow label will be described later.

The “Payload CRC” field of the layer 1 frame can realize link qualitymonitoring (as shown in (B) and (D) of FIG. 20) but can not be used forpath monitoring. Therefore, an OAM (Operating And Management) framewhich is shown in FIG. 22C can be employed for the path monitoringbetween the ingress point and the egress point in the network as shownin (B) and (E) of FIG. 20. The path monitoring can be executed byfilling the payload of the OAM frame shown in FIG. 22C with theso-called “PN pattern”, for example. The OAM frames can be transferredat the ends of the fixed intervals (125 μsec). When the OAM frames areused, the best effort IP transfer space length L which was used in theflow chart of FIG. 21 is decreased by the length of the OAM frame.

As described above, in the frame construction method in accordance withthe embodiment of the present invention, the STM layer 1 frames aretransferred at fixed periods (125 μsec). Bit synchronization isestablished in the physical layer, and byte synchronization and framesynchronization are established by use of the “Header CRC16” identifier,thereby the STM signals are necessarily transferred at fixed intervals(125 μsec) maintaining the end-to-end circuit quality monitoringfunctions (end-to-end performance monitoring functions).

Further, the STM signals, the ATM cells and the IP packets aretransferred by use of a common frame format, therefore, the differenttypes of information can be handled and managed in a networkconcurrently by a common method.

Therefore, the STM networks, the ATM networks and the IP networks whichhave been constructed separately and independently can be integrated orconstructed as a common or integrated network.

By the definition of the route label and the flow label as transferinformation for the IP layer 2 frames, IP packets can be transferredappropriately by simple procedures even when each link is composed oftwo or more wavelengths by means of WDM (Wavelength DivisionMultiplexing). The details of the transfer of the IP layer 1 frames byuse of the route label and the flow label will be described later.

In the following, a data transfer system for transferring a mixture ofthe STM traffic and the best effort traffic in accordance with theembodiment of the present invention will be explained in detail.

FIG. 12 is a schematic diagram showing an example of a network as a datatransfer system in accordance with the embodiment of the presentinvention. The network shown in FIG. 12 includes STM devices (STMswitch, STM transmission node, etc.) 1100 and 1111, ATM devices (ATMswitch, ATM crossconnect, etc.) 1101 and 1112, IP routers 1102 and 1113,edge nodes (ENs) 1103, 1106, 1108 and 1110, and core nodes (CNs) 1104,1105, 1107 and 1109.

The edge nodes 1103, 1106, 1108 and 1110 of the network are connected toconventional network devices such as the STM devices 1100 and 1111, theATM devices 1101 and 1112, the IP routers 1102 and 1113, etc. Therefore,the edge nodes 1103, 1106, 1108 and 1110 operate as the interfaces ofthe network to conventional network devices.

The edge node (1103, 1106, 1108, 1110) packs STM signals, ATM cells andIP packets in layer 2 frames (in layer 1 frames) as shown in FIGS. 4Athrough 4C and transmits the layer 1 frames to the network.

Meanwhile, the edge node (1103, 1106, 1108, 1110) receives andterminates layer 1 frames which are transferred from the network andextracts STM signals, ATM cells and IP packets from the layer 1 frames.The extracted STM signals, ATM cells and IP packets are transmitted tothe STM devices 1100 and 1111, the ATM devices 1101 and 1112, and the IProuters 1102 and 1113, respectively.

The core node (1104, 1105, 1107, 1109) terminates layer 1 frames andextracts layer 2 frames from the layer 1 frames. The core node (1104,1105, 1107, 1109) executes switching of the layer 2 frames based on theheader information of the extracted layer 2 frames. Thereafter, the corenode (1104, 1105, 1107, 1109) converts the layer 2 frames into layer 1frames and outputs the layer 1 frames to appropriate lines based on theheader information.

FIG. 15 is a block diagram showing an example of the internalcomposition of a transmission section of the edge node (1103, 1106,1108, 1110). In the following, the composition and the operation of thetransmission section of the edge node (1103, 1106, 1108, 1110) will bedescribed in detail referring to FIG. 15.

The transmission section of the edge node (1103, 1106, 1108, 1110) shownin FIG. 15 includes an IP packet reception section 1403, an ATM cellreception section 1404, an STM signal reception section 1405, a routelabel generation section 1406, a flow label generation section 1407, anIP layer 2 frame generation section 1408, an ATM layer 1 framegeneration section 1409, an STM layer 1 frame generation section 1410, atimer 1411, an IP layer 1 frame generation section 1412, a schedulersection 1413 and a frame multiplexing section 1414.

The STM signal reception section 1405 receives STM signals from an STMdevice 1402 for assembling STM layer 2 frames. The STM signal, whosedestination is recognized by provisioning, is an N-channel voice signal.The bit rate of each channel is set to 8 bit/125 μsec (64 Kbps),therefore, the bit rate of the STM signal becomes N×64 Kbps.

The STM signal reception section 1405 sends the STM signals to the STMlayer 1 frame generation section 1410. The STM layer 1 frame generationsection 1410 first generates STM layer 2 frames by forming STM layer 2frame payloads collecting the STM signals in units of 125 μsec andadding a layer 2 frame header including a route label to each STM layer2 frame payload, and thereafter generates STM layer 1 frames by adding“Packet Length” identifiers (indicating the length of the STM layer 1frame payload), “Priority” identifiers (indicating CBR (Constant BitRate) data transfer), “Protocol” identifiers (indicating STM), “FrameMode” identifiers (indicating “Single Frame”) and “Stuff” identifiers(indicating “No Stuffing”) to the STM layer 2 frames. Incidentally, theroute label of the STM layer 2 frame is generated by the STM layer 1frame generation section 1410 by provisioning. Concretely, STM framescontaining the STM signals are supplied from the STM device 1402, andthe destination of each STM signal is judged based on the position of atime slot (containing the STM signal) in the STM frame. The STM layer 2frame is generated by collecting STM signals for the same destination,and a route label corresponding to the destination is provided to theSTM layer 2 frame header, for example.

Subsequently, the STM layer 1 frame generation section 1410 conducts theCRC16 operation to the header of the generated STM layer 1 frame andadds the result to the bottom of the STM layer 1 frame header. Further,as an option, the STM layer 1 frame generation section 1410 conducts theCRC16 or CRC32 to the layer 1 frame payload and adds the result to therear end of the STM layer 1 frame.

The ATM cell reception section 1404 receives ATM cells from an ATMdevice 1401 for assembling ATM layer 2 frames and stores the ATM cellsin the ATM layer 1 frame generation section 1409.

The ATM layer 1 frame generation section 1409 first generates ATM layer2 frames by forming ATM layer 2 frame payloads by use of the stored ATMcells and adding a layer 2 frame header including a route label to eachATM layer 2 frame payload, and thereafter generates ATM layer 1 framesby adding “Packet Length” identifiers (indicating the length of the ATMlayer 1 frame payload), “Priority” identifiers (indicating types of theATM (CBR (Constant Bit Rate), UBR (Unspecified Bit Rate), etc.)),“Protocol” identifiers (indicating ATM), “Frame Mode” identifiers(indicating “Single Frame”) and “Stuff” identifiers (indicating “NoStuffing”) to the ATM layer 2 frames. Incidentally, the route label ofthe ATM layer 2 frame is generated by the ATM layer 1 frame generationsection 1409 based on the VPI/VCI of the ATM cell header, for example.

Subsequently, the ATM layer 1 frame generation section 1409 conducts theCRC16 operation to the header of the generated ATM layer 1 frame andadds the result to the bottom of the ATM layer 1 frame header. Further,as an option, the ATM layer 1 frame generation section 1409 conducts theCRC16 or CRC32 to the layer 1 frame payload and adds the result to therear end of the ATM layer 1 frame.

The IP packet reception section 1403 receives IP packets from an IProuter 1400 for assembling IP layer 2 frames and stores the IP packetsin the IP layer 2 frame generation section 1408. Meanwhile, headerinformation of the IP packets is sent to the route label generationsection 1406 and the flow label generation section 1407.

The route label generation section 1406 generates a route label based onthe destination IP address or based on the destination IP address andthe source IP address which are contained in the IP packet header, andsends the result (route label) to the IP layer 2 frame generationsection 1408.

The flow label generation section 1407 generates a flow label based onthe header information of the IP packet and sends the generated flowlabel to the IP layer 2 frame generation section 1408.

The IP layer 2 frame generation section 1408 generates IP layer 2 framesby use of the IP packets, the route labels and the flow labels. Thegenerated IP layer 2 frames are sent to the IP layer 1 frame generationsection 1412 and stored therein.

The IP layer 1 frame generation section 1412 separates the stored IPlayer 2 frames into primary IP layer 2 frames and best effort IP layer 2frames. Whether an IP layer 2 frame is a primary IP layer 2 frame or abest effort IP layer 2 frame can be determined by referring to the COS(Class Of Service) identifier of the IP packet header, or by judgingwhether or not the IP packet header includes registered IP addressinformation concerning primary IP, for example. The IP layer 1 framegeneration section 1412 generates primary IP layer 1 frames and besteffort IP layer 1 frames by use of the primary IP layer 2 frames and thebest effort IP layer 2 frames respectively, and outputs the primary IPlayer 1 frames to the frame multiplexing section 1414 with higherpriority than the best effort IP layer 1 frames.

The IP layer 1 frame generation section 1412 partitions the best effortIP layer 1 frame into the BOM frame, the COM frames and the EOM frameaccording to the method which has been described referring to the flowchart of FIG. 21. The IP layer 1 frame generation section 1412 insertsthe stuff data to the best effort IP layer 1 frame if necessaryaccording to the above method.

The judgment on whether the best effort IP layer 1 frame should betransmitted as a single frame or should be partitioned into a BOM frame,COM frames and an EOM frame, and the judgment on whether the stuff datashould be inserted or not are conducted depending on the length L of thebest effort IP transfer space, as explained referring to the flow chartof FIG. 21.

The IP layer 1 frame generation section 1412 generates a “Packet Length”identifier (indicating the length of the best effort IP layer 1 framepayload), a “Priority” identifier (indicating low priority), a“Protocol” identifier (indicating IP), a “Frame Mode” identifier(indicating a single frame, a BOM frame, a COM frame or an EOM frame)and a “Stuff” identifier (indicating whether or not stuff data exists)as the best effort IP layer 1 frame header.

Subsequently, the IP layer 1 frame generation section 1412 conducts theCRC16 operation to the generated best effort IP layer 1 frame header andadds the result (“Header CRC16” identifier) to the bottom of the besteffort IP layer 1 frame header.

In the case where the stuff data is inserted in the best effort IP layer1 frame, the IP layer 1 frame generation section 1412 adds the “StuffingLength” identifier (indicating the length of the stuff data) after the“Header CRC16” identifier and inserts the stuff data at the bottom ofthe best effort IP layer 1 frame payload as shown in FIG. 7.

Further, as an option, the IP layer 1 frame generation section 1412conducts the CRC16 or CRC32 to the best effort IP layer 1 frame payloadand adds the result to the rear end of the best effort IP layer 1 frame.

The best effort IP layer 1 frames generated by the IP layer 1 framegeneration section 1412 is outputted to the frame multiplexing section1414 with lower priority than the primary IP layer 1 frames.Incidentally, for the primary IP layer 1 frames, the IP layer 1 framegeneration section 1412 generates a “Packet Length” identifier(indicating the length of the primary IP layer 1 frame payload), a“Priority” identifier (indicating high priority), a “Protocol”identifier (indicating IP), a “Frame Mode” identifier (indicating asingle frame), a “Stuff” identifier (indicating “No Stuffing”) and a“Header CRC16” identifier. The primary IP layer 1 frames as singleframes are outputted to the frame multiplexing section 1414 with higherpriority than the best effort IP layer 1 frames.

The scheduler section 1413 instructs the STM layer 1 frame generationsection 1410 to output an STM layer 1 frame to the frame multiplexingsection 1414 periodically (125 μsec) based on internal time which isclocked by the timer 1411.

After letting the STM layer 1 frame generation section 1410 output theSTM layer 1 frame to the frame multiplexing section 1414, the schedulersection 1413 instructs the ATM layer 1 frame generation section 1409 tooutput one or more ATM layer 1 frames stored therein to the framemultiplexing section 1414.

After letting the ATM layer 1 frame generation section 1409 output theATM layer 1 frames to the frame multiplexing section 1414, the schedulersection 1413 instructs the IP layer 1 frame generation section 1412 tooutput one or more primary IP layer 1 frames stored therein to the framemultiplexing section 1414 as single frames.

After letting the IP layer 1 frame generation section 1412 output theprimary IP layer 1 frames to the frame multiplexing section 1414, thescheduler section 1413 instructs the IP layer 1 frame generation section1412 to output a best effort IP layer 1 frame stored therein to theframe multiplexing section 1414 as a single frame, a BOM frame, a COMframe or an EOM frame. The IP layer 1 frame generation section 1412outputs one or more best effort IP layer 1 frames according to thealgorithm which has been explained referring to the flow chart of FIG.21.

The frame multiplexing section 1414 receives the STM layer 1 frames, theATM layer 1 frames, the primary IP layer 1 frames and the best effort IPlayer 1 frames which are supplied from the STM layer 1 frame generationsection 1410, the ATM layer 1 frame generation section 1409 and the IPlayer 1 frame generation section 1412 according to the instructions ofthe scheduler section 1413, and frame multiplexes the layer 1 frames asshown in FIGS. 10 and 11. The frame-multiplexed layer 1 frames areoutputted by the frame multiplexing section 1414 to a transmission line(to a core node (1104, 1105, 1107, 1109)).

FIG. 16 is a block diagram showing an example of the internalcomposition of a reception section of the edge node (1103, 1106, 1108,1110). In the following, the composition and the operation of thereception section of the edge node (1103, 1106, 1108, 1110) will bedescribed in detail referring to FIG. 16.

The reception section of the edge node (1103, 1106, 1108, 1110) shown inFIG. 16 includes an IP packet transmission section 1503, an ATM celltransmission section 1504, an STM signal transmission section 1505,frame termination sections 1506, 1507 and 1508, and a frame separationsection 1509.

The frame separation section 1509 establishes bit synchronization, bytesynchronization and frame synchronization by use of the layer 1 frameheaders.

After establishing the bit synchronization, the byte synchronization andthe frame synchronization, the frame separation section 1509 refers tothe “Protocol” identifier contained in the header of a layer 1 frame andthereby judges whether the data contained in the payload of the layer 1frame is an STM signal, an ATM cell or an IP packet.

Subsequently, the frame separation section 1509 refers to the “PacketLength” identifier of the layer 1 frame header and thereby grasps thetotal length and the rear end of the layer 1 frame payload.

When the layer 1 frame is an STM layer 1 frame, the frame separationsection 1509 sends the STM layer 1 frame to the frame terminationsection 1508. When the layer 1 frame is an ATM layer 1 frame, the frameseparation section 1509 sends the ATM layer 1 frame to the frametermination section 1507. When the layer 1 frame is an IP layer 1 frame,the frame separation section 1509 sends the IP layer 1 frame to theframe termination section 1506.

The frame termination section 1508 extracts STM signals from the layer 1frames and sends the extracted STM signals to the STM signaltransmission section 1505. The STM signal transmission section 1505transmits the STM signals to an STM device 1502.

The frame termination section 1507 extracts ATM cells from the layer 1frames and sends the extracted ATM cells to the ATM cell transmissionsection 1504. The ATM cell transmission section 1504 transmits the ATMcells to an ATM device 1501.

The frame termination section 1506 extracts an IP layer 2 frame from theIP layer 1 frame if the IP layer 1 frame is a single frame. If the stuffdata has been inserted in the IP layer 2 frame, the frame terminationsection 1506 removes the stuff data from the IP layer 2 frame.Subsequently, the termination section 1506 extracts an IP packet fromthe IP layer 2 frame and sends the extracted IP packet to the IP packettransmission section 1503. The IP packet transmission section 1503transmits the IP packet to an IP router 1500.

If the layer 1 frame is a BOM frame or a COM frame, the frametermination section 1506 stores the BOM/COM frame until an EOM frame issupplied from the frame separation section 1509. When the EOM frame issupplied from the frame separation section 1509, the frame terminationsection 1506 reconstructs a layer 2 frame by connecting the payloads ofthe BOM frame, the COM frames and the EOM frame. In the reconstructionof the layer 2 frame, the frame termination section 1506 judges whetheror not the stuff data has been inserted in each of the layer 1 frames.If the stuff data has been inserted in a layer 1 frame, the frametermination section 1506 removes the stuff data from the layer 1 frame.

Subsequently, the frame termination section 1506 extracts an IP packetfrom the reconstructed layer 2 frame and sends the extracted IP packetto the IP packet transmission section 1503. The IP packet transmissionsection 1503 transmits the IP packet to the IP router 1500.

FIG. 17 is a block diagram showing an example of the internalcomposition of the core node (1104, 1105, 1107, 1109). In the following,the composition and the operation of the core node (1104, 1105, 1107,1109) will be described in detail referring to FIG. 17.

The core node (1104, 1105, 1107, 1109) shown in FIG. 17 includesreception sections 1600 and 1601, a layer 2 frame switch 1602, andtransmission sections 1603 and 1604.

The reception section (1600, 1601) establishes byte synchronization andframe synchronization with regard to each input line by use of the“Header CRC16” identifiers in the layer 1 frame headers.

The layer 2 frame switch 1602 determines an appropriate output line(output port) for each frame based on the label information of the layer2 frame header and thereby conducts frame switching. The transmissionsection (1603, 1604) reconstructs layer 1 frames for the transmission ofthe layer 2 frames into the appropriate output line.

FIG. 18 is a block diagram showing an example of the internalcomposition of the reception section (1600, 1601) of the core node(1104, 1105, 1107, 1109). In the following, the composition and theoperation of the reception section (1600, 1601) of the core node (1104,1105, 1107, 1109) will be described in detail referring to FIG. 18.

The reception section (1600, 1601) of the core node (1104, 1105, 1107,1109) shown in FIG. 18 includes a layer 1 termination section 1700, anSTM layer 2 termination section 1701, an ATM layer 2 termination section1702, an IP layer 2 termination section 1703, a frame multiplexingsection 1704 and a priority processing scheduler 1705.

The layer 1 termination section 1700 terminates layer 1 frames which aresupplied from a transmission line. The layer 1 termination section 1700determines the type (STM, ATM or IP packet) of the layer 1 frame basedon the “Protocol” identifier in the layer 1 frame header, and sends thelayer 1 frame to the STM layer 2 termination section 1701, the ATM layer2 termination section 1702 or the IP layer 2 termination section 1703depending on the type of the layer 1 frame.

The STM layer 2 termination section 1701 extracts an STM layer 2 framefrom the STM layer 1 frame supplied from the layer 1 termination section1700. In the same way, the ATM layer 2 termination section 1702 extractsan ATM layer 2 frame from the ATM layer 1 frame supplied from the layer1 termination section 1700.

The IP layer 2 termination section 1703 extracts an IP layer 2 framefrom the IP layer 1 frame supplied from the layer 1 termination section1700 if the IP layer 1 frame is a single frame. If the IP layer 1 frameis a BOM frame or a COM frame, the IP layer 2 termination section 1703stores the BOM/COM frame until an EOM frame is supplied from the layer 1termination section 1700.

When the EOM frame is supplied from the layer 1 termination section1700, the IP layer 2 termination section 1703 reconstructs an IP layer 2frame by connecting the payloads of the BOM frame, the COM frames andthe EOM frame.

In the extraction of the IP layer 2 frame from the IP layer 1 frame, theIP layer 2 termination section 1703 refers to the “Stuff” identifier ofthe IP layer 1 frame header and thereby judges whether or not the stuffdata has been inserted in the IP layer 1 frame. If the stuff data hasbeen inserted in the IP layer 1 frame, the IP layer 2 terminationsection 1703 removes the stuff data (of a length which is described inthe “Stuffing Length” identifier) from the payload of the IP layer 1frame.

The priority processing scheduler 1705 grasps the presence or absence oflayer 2 frames stored in the STM layer 2 termination section 1701, theATM layer 2 termination section 1702 and the IP layer 2 terminationsection 1703 and conducts the management of priority processing.

If an STM layer 2 frame, to be handled with the highest priority, existsin the STM layer 2 termination section 1701, the priority processingscheduler 1705 instructs the frame multiplexing section 1704 to read outthe STM layer 2 frame with the highest priority.

Thereafter, if one or more ATM layer 2 frames, to be handled with thesecond priority, exist in the ATM layer 2 termination section 1702, thepriority processing scheduler 1705 instructs the frame multiplexingsection 1704 to read out the ATM layer 2 frames.

Thereafter, if one or more primary layer 2 frames, to be handled withthe third priority, exist in the IP layer 2 termination section 1703,the priority processing scheduler 1705 instructs the frame multiplexingsection 1704 to read out the primary IP layer 2 frames from the IP layer2 termination section 1703 if no ATM layer 2 frame exists in the ATMlayer 2 termination section 1702.

The best effort IP layer 2 frame is a layer 2 frame of the lowestpriority, therefore, the priority processing scheduler 1705 instructsthe frame multiplexing section 1704 to read out the best effort IP layer2 frames from the IP layer 2 termination section 1703 only when there isno STM layer 2 frame, ATM layer 2 frame nor primary IP layer 2 frame inthe reception section (1600, 1601).

The frame multiplexing section 1704 reads out the layer 2 frames fromthe STM layer 2 termination section 1701, the ATM layer 2 terminationsection 1702 and the IP layer 2 termination section 1703 according tothe instructions of the priority processing scheduler 1705 and sends thelayer 2 frames to the layer 2 frame switch 1602.

FIG. 19 is a block diagram showing an example of the internalcomposition of the transmission section (1603, 1604) of the core node(1104, 1105, 1107, 1109). In the following, the composition and theoperation of the transmission section (1603, 1604) of the core node(1104, 1105, 1107, 1109) will be described in detail referring to FIG.19.

The transmission section (1603, 1604) of the core node (1104, 1105,1107, 1109) shown in FIG. 19 includes a frame multiplexing section 1800,an STM layer 1 frame generation section 1801, an ATM layer 1 framegeneration section 1802, an IP layer 1 frame generation section 1803, aframe separation section 1804 and a transmission scheduler 1805.

The frame separation section 1804 receives the layer 2 frame from thelayer 2 frame switch 1602 and sends the layer 2 frame to the STM layer 1frame generation section 1801, the ATM layer 1 frame generation section1802 or the IP layer 1 frame generation section 1803 depending on theprotocol (STM, ATM, IP, etc.) of the layer 2 frame. Incidentally,information concerning the protocol of each layer 2 frame is suppliedfrom the reception section (1600, 1601) via the layer 2 frame switch1602 as control information. The control information can be transferredin the core node (1104, 1105, 1107, 1109) by multiplexing with the layer2 frames.

The transmission scheduler 1805 grasps the presence or absence of layer2 frames stored in the STM layer 1 frame generation section 1801, theATM layer 1 frame generation section 1802 and the IP layer 1 framegeneration section 1803 and conducts the management of priorityprocessing.

The transmission scheduler 1805 instructs the STM layer 1 framegeneration section 1801 to output an STM layer 1 frame periodically (125μsec).

The STM layer 1 frame generation section 1801 converts the stored STMlayer 2 frame into an STM layer 1 frame and sends the STM layer 1 frameto the frame multiplexing section 1800. Incidentally, informationnecessary for generating the layer 1 frame header can be transferred inthe core node (1104, 1105, 1107, 1109) as the aforementioned controlinformation.

In the conversion from the STM layer 2 frame to the STM layer 1 frame,the STM layer 1 frame generation section 1801 inserts the STM layer 2frame in the payload of the STM layer 1 frame and inserts a “PacketLength” identifier, a “Priority” identifier (indicating CBR (ConstantBit Rate) data transfer), a “Protocol” identifier (indicating STM), a“Frame Mode” identifier (indicating “Single Frame”) and a “Stuff”identifier (indicating “No Stuffing”) in the header of the STM layer 1frame. The STM layer 1 frame generation section 1801 conducts CRC16operation to the above STM layer 1 frame header and adds the result tothe bottom of the STM layer 1 frame header. Further, as an option, theSTM layer 1 frame generation section 1801 conducts the CRC16 or CRC32 tothe STM layer 1 frame payload and adds the result to the rear end of theSTM layer 1 frame.

The ATM layer 1 frame generation section 1802 converts the stored ATMlayer 2 frame into an ATM layer 1 frame by inserting the ATM layer 2frame in the payload of the ATM layer 1 frame and inserting a “PacketLength” identifier, a “Priority” identifier (indicating the type of ATM(CBR, UBR, etc.)), a “Protocol” identifier (indicating ATM), a “FrameMode” identifier (indicating “Single Frame”) and a “Stuff” identifier(indicating “No Stuffing”) in the header of the ATM layer 1 frame. TheATM layer 1 frame generation section 1802 conducts CRC16 operation tothe above ATM layer 1 frame header and adds the result to the bottom ofthe ATM layer 1 frame header. Further, as an option, the ATM layer 1frame generation section 1802 conducts the CRC16 or CRC32 to the ATMlayer 1 frame payload and adds the result to the rear end of the ATMlayer 1 frame.

The IP layer 1 frame generation section 1803 separates the IP layer 2frames into primary IP layer 2 frames and best effort IP layer 2 frames,generates primary IP layer 1 frames and best effort IP layer 1 frames byuse of the primary IP layer 2 frames and the best effort IP layer 2frames respectively, and outputs the primary IP layer 1 frames and thebest effort IP layer 1 frames to the frame multiplexing section 1800giving higher priority to the primary IP layer 1 frames.

The IP layer 1 frame generation section 1803 partitions the best effortIP layer 1 frame (or the best effort IP layer 2 frame) into segments anddistributes to a BOM frame, COM frames and an EOM frame if necessaryaccording to the method which has been described referring to FIG. 21.The IP layer 1 frame generation section 1803 inserts the stuff data tothe best effort IP layer 1 frame if necessary according to the abovemethod.

The judgment on whether the best effort IP layer 1 frame should betransmitted as a single frame or should be partitioned into a BOM frame,COM frames and an EOM frame, and the judgment on whether the stuff datashould be inserted or not are conducted depending on the length L of thebest effort IP transfer space, as explained referring to FIG. 21.

The IP layer 1 frame generation section 1803 generates a “Packet Length”identifier (indicating the length of the best effort IP layer 1 framepayload), a “Priority” identifier (indicating low priority), a“Protocol” identifier (indicating IP), a “Frame Mode” identifier(indicating a single frame, a BOM frame, a COM frame or an EOM frame)and a “Stuff” identifier (indicating whether or not stuff data exists)as the best effort IP layer 1 frame header.

Subsequently, the IP layer 1 frame generation section 1803 conducts theCRC16 operation to the generated best effort IP layer 1 frame header andadds the result (“Header CRC16” identifier) to the bottom of the besteffort IP layer 1 frame header.

In the case where the stuff data is inserted in the best effort IP layer1 frame, the IP layer 1 frame generation section 1803 adds the “StuffingLength” identifier (indicating the length of the stuff data) after the“Header CRC16” identifier and inserts the stuff data at the bottom ofthe best effort IP layer 1 frame payload as shown in FIG. 7.

Further, as an option, the IP layer 1 frame generation section 1803conducts the CRC16 or CRC32 to the best effort IP layer 1 frame payloadand adds the result to the rear end of the best effort IP layer 1 frame.

The best effort IP layer 1 frames generated by the IP layer 1 framegeneration section 1803 is outputted to the frame multiplexing section1800 with lower priority than the primary IP layer 1 frames.Incidentally, for the primary IP layer 1 frames, the IP layer 1 framegeneration section 1803 generates a “Packet Length” identifier(indicating the length of the primary IP layer 1 frame payload), a“Priority” identifier (indicating high priority), a “Protocol”identifier (indicating IP), a “Frame Mode” identifier (indicating asingle frame), a “Stuff” identifier (indicating “No Stuffing”) and a“Header CRC16” identifier. The primary IP layer 1 frames as singleframes are outputted to the frame multiplexing section 1800 with higherpriority than the best effort IP layer 1 frames.

The transmission scheduler 1805 instructs the STM layer 1 framegeneration section 1801 to output an STM layer 1 frame to the framemultiplexing section 1800 periodically (125 μsec).

After letting the STM layer 1 frame generation section 1801 output theSTM layer 1 frame to the frame multiplexing section 1800, thetransmission scheduler 1805 instructs the ATM layer 1 frame generationsection 1801 to output one or more ATM layer 1 frames stored therein tothe frame multiplexing section 1414.

After letting the ATM layer 1 frame generation section 1802 output theATM layer 1 frames to the frame multiplexing section 1800, thetransmission scheduler 1805 instructs the IP layer 1 frame generationsection 1803 to output one or more primary IP layer 1 frames storedtherein to the frame multiplexing section 1800 as single frames.

After letting the IP layer 1 frame generation section 1803 output theprimary IP layer 1 frames to the frame multiplexing section 1800, thetransmission scheduler 1805 instructs the IP layer 1 frame generationsection 1803 to output a best effort IP layer 1 frame stored therein tothe frame multiplexing section 1800 as a single frame, a BOM frame, aCOM frame or an EOM frame. The IP layer 1 frame generation section 1803outputs one or more best effort IP layer 1 frames according to thealgorithm which has been explained referring to the flow chart of FIG.21.

The frame multiplexing section 1800 receives the STM layer 1 frames, theATM layer 1 frames, the primary IP layer 1 frames and the best effort IPlayer 1 frames supplied from the STM layer 1 frame generation section1801, the ATM layer 1 frame generation section 1802 and the IP layer 1frame generation section 1803, and frame multiplexes the layer 1 framesas shown in FIGS. 10 and 11. The frame-multiplexed layer 1 frames areoutputted by the frame multiplexing section 1800 to a transmission line.

FIG. 20 is a schematic diagram showing link monitoring and pathmonitoring which are conducted in this embodiment. FIG. 20 shows anexample of frame transfer between edge nodes 1900 and 1904 via corenodes 1901, 1902 and 1903.

As shown (B) of FIG. 20, link monitoring with regard to each linkbetween two nodes is conducted by each node (1901, 1902, 1903, 1904) byreferring to the “Payload CRC” field of each layer 1 frame which isshown in (D) of FIG. 20.

As shown (C) of FIG. 20, path monitoring with regard to a path from theingress point to the egress point can be conducted by the edge node 1904at the egress point by referring to the OAM frame which is shown in (E)of FIG. 20 (see FIG. 22C). As mentioned before, the so-called PN patterncan be packed in the payload of the OAM frame, for example.

As described above, in the data transfer system and the frameconstruction devices in accordance with the embodiment of the presentinvention, the STM layer 1 frames are transferred at fixed periods (125μsec). Bit synchronization is established in the physical layer, andbyte synchronization and frame synchronization are established by use ofthe “Header CRC16” identifier, thereby the STM signals are necessarilytransferred at fixed intervals (125 μsec) maintaining the end-to-endcircuit quality monitoring functions (end-to-end performance monitoringfunctions).

Further, the STM signals, the ATM cells and the IP packets aretransferred by use of a common frame format, therefore, the differenttypes of information can be handled and managed in a networkconcurrently by a common method.

Especially, the core node (1104, 1105, 1107, 1109) establishes the bitsynchronization, the byte synchronization and the frame synchronizationby referring to the layer 1 frame headers, and the STM layer 1 frames,the ATM layer 1 frames and the IP layer 1 frames are outputted toappropriate output lines by use of the layer 2 frame switch 1602.

Therefore, the STM networks, the ATM networks and the IP networks whichhave been constructed separately and independently can be integrated orconstructed as a common or integrated network.

By the definition of the route label and the flow label as transferinformation for the IP layer 2 frames, IP packets can be transferredappropriately by simple procedures even when each link is composed oftwo or more wavelengths by means of WDM (Wavelength DivisionMultiplexing).

In the following, the operation of the data transfer system inaccordance with the embodiment of the present invention for transferringa mixture of the STM traffic and the best effort traffic will beexplained more in detail.

First, the transfer of STM signals in the data transfer system of FIG.12 will be explained in detail.

Referring to FIG. 15, in the transmission section of the edge node 1103,the STM signal reception section 1405 receives STM frames (containingSTM signals) from the STM device 1402 (1100) and stores the STM frames.The STM signal reception section 1405 terminates the layer 1 which isused between the STM device 1402 and the edge node 1103, extracts theSTM signals from the STM frames, and sends the STM signals to the STMlayer 1 frame generation section 1410.

The layer 1 between the STM device 1100 (1402) and the edge node 1103 isimplemented by conventional specifications such as SDH (SynchronousDigital Hierarchy), PDH (Plesiochronous Digital Hierarchy), etc.

The STM signals are converted into layer 2 frames by the STM layer 1frame generation section 1410. Concretely, the 64 Kbps×N channel voicesignal (8 bits/125 μsec for each channel), whose destination isrecognized by the STM device 1100 (1402) by provisioning, is packed inthe layer 2 frame payload. A layer 2 frame header corresponding to thedestination of the STM signals is added to the layer 2 frame payload bythe STM layer 1 frame generation section 1410, thereby the STM layer 2frame which is shown in FIG. 4B is generated.

Subsequently, the STM layer 1 frame generation section 1410 generates anSTM layer 1 frame header including the “Packet Length” identifier(indicating the length of the STM layer 1 frame payload), the “Priority”identifier (indicating CBR data transfer), the “Protocol” identifier(indicating STM), the “Frame Mode” identifier (indicating “SingleFrame”) and the “Stuff” identifier (indicating “No Stuffing”), and addsthe layer 1 frame header to the layer 2 frame. Incidentally, in the STMlayer 1 frames, the “Frame Mode” identifier is always set to “00”(Single Frame) and the “Stuff” identifier is always set to “0” (NoStuffing) (see FIGS. 5B and 5C).

The CRC16 operation is conducted to the layer 1 frame header and theresult is added to the bottom of the layer 1 frame header. As an option,the CRC16 or CRC32 is conducted to the layer 1 frame payload and theresult is added to the rear end of the layer 1 frame.

By the above process, an STM layer 1 frame having the basic frame formatshown in FIG. 2 is formed. More concretely, the layer 2 frame shown inFIG. 3A (containing the layer 2 frame header and the layer 2 framepayload in which the STM signals are packed) is packed in the STM layer1 frame payload as shown in FIG. 4B, and the above identifiers shown inFIG. 5A are packed in the STM layer 1 frame header.

The scheduler section 1413 of the edge node 1103 grasps whether or notlayer 1 frames to be transferred exist in the STM layer 1 framegeneration section 1410, the ATM layer 1 frame generation section 1409and the IP layer 1 frame generation section 1412.

When an STM layer 1 frame to be transferred is stored in the STM layer 1frame generation section 1410, the scheduler section 1413 instructs theSTM layer 1 frame generation section 1410 to output STM layer 1 framesperiodically (125 μsec). According to the instructions of the schedulersection 1413, the STM layer 1 frame generation section 1410 outputs theSTM layer 1 frames to the frame multiplexing section 1414 periodically(125 μsec).

The frame multiplexing section 1414 frame multiplexes the STM layer 1frames from the STM layer 1 frame generation section 1410 with layer 1frames supplied from the ATM layer 1 frame generation section 1409 andthe IP layer 1 frame generation section 1412, and transmits theframe-multiplexed layer 1 frames to a transmission line (to the corenode 1104).

The layer 1 frames transmitted by the edge node 1103 to the transmissionline are terminated by the layer 1 termination section 1700 of thereception section (1600, 1601) of the core node 1104.

The layer 1 termination section 1700 establishes byte synchronizationand frame synchronization with regard to each input line by use of the“Header CRC16” identifiers of the headers of the layer 1 frames. Thelayer 1 termination section 1700 establishes the frame synchronizationby checking the “Header CRC16” identifier. If the result of the check is“0”, the layer 1 termination section 1700 judges that the framesynchronization has been established.

The layer 1 termination section 1700 refers to the “Packet Length”identifier in the layer 1 frame header in order to establish framesynchronization with the next frame, thereby the reference of the“Header CRC16” identifier contained in the next layer 1 frame header isenabled.

Subsequently, the layer 1 termination section 1700 refers to the“Protocol” identifier in the layer 1 frame header and thereby judges thetype (STM, ATM, IP) of the layer 2 frame contained in the payload of thelayer 1 frame.

Layer 1 frames that are judged by the layer 1 termination section 1700as STM layer 1 frames are sent to the STM layer 2 termination section1701. The STM layer 2 termination section 1701 which received the STMlayer 1 frames extracts STM layer 2 frames from the STM layer 1 frames.

The priority processing scheduler 1705 checks whether or not an STMlayer 2 frame exists in the STM layer 2 termination section 1701.Incidentally, the “Priority” identifiers of the STM layer 1 frames havebeen set higher in comparison with layer 1 frames of other types.

Therefore, when an STM layer 2 frame exists in the STM layer 2termination section 1701, the priority processing scheduler 1705instructs the STM layer 2 termination section 1701 to output the STMlayer 2 frames to the frame multiplexing section 1704.

According to the instructions of the priority processing scheduler 1705,the STM layer 2 termination section 1701 outputs the STM layer 2 framesto the frame multiplexing section 1704. The frame multiplexing section1704 frame multiplexes the STM layer 2 frames from the STM layer 2termination section 1701 with ATM layer 2 frames supplied from the ATMlayer 2 termination section 1702 and IP layer 2 frames supplied from theIP layer 2 termination section 1703, and sends the frame-multiplexedlayer 2 frames to the layer 2 frame switch 1602.

The layer 2 frame switch 1602 transmits the layer 2 frames toappropriate output lines (transmission section 1603 or 1604) based onthe label information contained in the layer 2 frame headers.

In the transmission section (1603, 1604) of the core node 1104, theframe separation section 1804 judges the protocol type (STM, ATM, IP) ofeach layer 2 frame supplied from the layer 2 frame switch 1602 based oncontrol information which is transferred in the core node 1104. Layer 2frames that are judged by the frame separation section 1804 as STM layer2 frames are sent to the STM layer 1 frame generation section 1801.

The transmission scheduler 1805 checks whether or not an STM layer 2frame exists in the STM layer 1 frame generation section 1801. If an STMlayer 2 frame exists in the STM layer 1 frame generation section 1801,the transmission scheduler 1805 instructs the STM layer 1 framegeneration section 1801 to output STM layer 1 frames to the framemultiplexing section 1800 periodically (125 μsec). Incidentally, thetransfer of the STM layer 1 frames is conducted with higher prioritythan layer 1 frames of other types.

According to the instructions of the transmission scheduler 1805, theSTM layer 1 frame generation section 1801 converts the stored STM layer2 frames into STM layer 1 frames and outputs the STM layer 1 frames tothe frame multiplexing section 1800 periodically (125 μsec). The framemultiplexing section 1800 frame multiplexes the STM layer 1 frames fromthe STM layer 1 frame generation section 1801 with ATM layer 1 framessupplied from the ATM layer 1 frame generation section 1802 and IP layer1 frames supplied from the IP layer 1 frame generation section 1803, andtransmits the frame-multiplexed layer 1 frames to a transmission line(to the core node 1105).

Thereafter, the STM layer 1 frames are transferred to the edge node 1110shown in FIG. 12 via the core nodes 1105 and 1109.

The edge node 1110 receives the layer 1 frames from the core node 1109.In the reception section of the edge node 1110, the frame separationsection 1509 establishes bit synchronization, byte synchronization andframe synchronization by use of the headers of the layer 1 frames.

After the establishment of the frame synchronization, the frameseparation section 1509 refers to the “Protocol” identifier of the layer1 frame and thereby judges whether the data contained in the payload ofthe layer 1 frame is an STM layer 2 frame, an ATM layer 2 frame or an IPlayer 2 frame.

The frame separation section 1509 also refers to the “Packet Length”identifier of the layer 1 frame header and thereby grasps the totallength and the rear end of the layer 1 frame payload. In the case wherethe data contained in the layer 1 frame payload is an STM layer 2 frame,the frame separation section 1509 sends the layer 1 frame to the frametermination section 1508.

The frame termination section 1508 extracts STM signals from the STMlayer 1 frame and sends the STM signals to the STM signal transmissionsection 1505. The STM signals are transferred by the STM signaltransmission section 1505 to the STM device 1111 (1502).

As explained above, the STM layer 1 frames containing the STM signalsare transferred to the destination at precisely fixed intervals (125μsec) maintaining the end-to-end circuit quality monitoring functions(end-to-end performance monitoring functions).

Next, the transfer of ATM cells in the data transfer system of FIG. 12will be explained in detail.

Referring to FIG. 15, in the transmission section of the edge node 1103,the ATM cell reception section 1404 receives ATM cells from the ATMdevice 1101 (1401). The ATM cell reception section 1404 terminates thelayer 1 which is used between the ATM device 1101 (1401) and the edgenode 1103, establishes ATM cell synchronization, and sends the ATM cellsto the ATM layer 1 frame generation section 1409.

The ATM layer 1 frame generation section 1409 collects ATM cellscorresponding to the same VP (Virtual Path) and thereby constructs ATMlayer 2 frames which are shown in FIG. 4A. As shown in FIG. 4A, the ATMlayer 2 frame contains a plurality of ATM cells. The ATM layer 1 framegeneration section 1409 generates an ATM layer 2 frame header(containing a route label) and adds the ATM layer 2 frame header to theATM layer 2 frame payload.

The ATM layer 1 frame generation section 1409 generates a layer 1 frameheader including the “Packet Length” identifier (indicating the lengthof the ATM layer 1 frame payload), the “Priority” identifier (indicatingthe type (CBR, UBR, etc.) of ATM), the “Protocol” identifier (indicatingATM), the “Frame Mode” identifier (indicating “Single Frame”) and the“Stuff” identifier (indicating “No Stuffing”), and adds the layer 1frame header to the layer 2 frame. Incidentally, in the ATM layer 1frames, the “Frame Mode” identifier is always set to “00” (Single Frame)and the “Stuff” identifier is always set to “0” (No Stuffing) (see FIGS.5B and 5C).

The ATM layer 1 frame generation section 1409 conducts the CRC16operation to the ATM layer 1 frame header and adds the result to thebottom of the ATM layer 1 frame header. Further, the ATM layer 1 framegeneration section 1409 conducts the CRC16 or CRC32 to the ATM layer 1frame payload and adds the result to the rear end of the ATM layer 1frame.

After the transfer of the STM layer 1 frame from the STM layer 1 framegeneration section 1410 to the frame multiplexing section 1414, thescheduler section 1413 instructs the ATM layer 1 frame generationsection 1409 to output the ATM layer 1 frames to the frame multiplexingsection 1414. According to the instruction, the ATM layer 1 framegeneration section 1409 outputs the ATM layer 1 frames to the framemultiplexing section 1414.

The frame multiplexing section 1414 frame multiplexes the ATM layer 1frames from the ATM layer 1 frame generation section 1409 with STM layer1 frames supplied from the STM layer 1 frame generation section 1410 andIP layer 1 frames supplied from the IP layer 1 frame generation section1412, and transmits the frame-multiplexed layer 1 frames to thetransmission line (to the core node 1104).

In the reception section (1600, 1601) of the core node 1104, the layer 1termination section 1700 receives the frame-multiplexed layer 1 framesand establishes byte synchronization and frame synchronization withregard to each input line by checking the “Header CRC16” identifier ofeach layer 1 frame header.

The layer 1 termination section 1700 refers to the “Protocol”identifiers of the headers of the layer 1 frames, thereby extracts ATMlayer 1 frames, and sends the ATM layer 1 frames to the ATM layer 2termination section 1702. The ATM layer 2 termination section 1702 whichreceived the ATM layer 1 frame extracts the ATM layer 2 frame from theATM layer 1 frame.

According to the instruction of the priority processing scheduler 1705,the ATM layer 2 frame stored in the ATM layer 2 termination section 1702is outputted to the frame multiplexing section 1704 after the transferof an STM layer 2 frame from the STM layer 2 termination section 1701 tothe frame multiplexing section 1704.

The frame multiplexing section 1704 frame multiplexes the ATM layer 2frames from the ATM layer 2 termination section 1702 with STM layer 2frames supplied from the STM layer 2 termination section 1701 and IPlayer 2 frames supplied from the IP layer 2 termination section 1703,and sends the frame-multiplexed layer 2 frames to the layer 2 frameswitch 1602 of the core node 1104.

The layer 2 frame switch 1602 outputs the layer 2 frames to appropriatelines (transmission section 1603 or 1604) based on the label informationwhich is contained in the layer 2 frame headers.

In the transmission section (1603, 1604) of the core node 1104, theframe separation section 1804 separates the frame-multiplexed layer 2frames depending on their protocols (by use of the aforementionedcontrol information), extracts ATM layer 2 frames, and sends the ATMlayer 2 frames to the ATM layer 1 frame generation section 1802.

The ATM layer 1 frame generation section 1802 generates ATM layer 1frames by use of the ATM layer 2 frames supplied from the frameseparation section 1804 and the aforementioned control information.

The transmission scheduler 1805 instructs the ATM layer 1 framegeneration section 1802 to output the ATM layer 1 frame to the framemultiplexing section 1800 after each of the periodical instructions (125μL sec) to the STM layer 1 frame generation section 1801 to output STMlayer 1 frames to the frame multiplexing section 1800.

According to the instructions of the transmission scheduler 1805, theATM layer 1 frame generation section 1802 outputs the generated STMlayer 1 frame to the frame multiplexing section 1800. The framemultiplexing section 1800 frame multiplexes the ATM layer 1 frames fromthe ATM layer 1 frame generation section 1802 with STM layer 1 framessupplied from the STM layer 1 frame generation section 1801 and IP layer1 frames supplied from the IP layer 1 frame generation section 1803, andtransmits the frame-multiplexed layer 1 frames to a transmission line(to the core node 1105).

Thereafter, the ATM layer 1 frames are transferred to the edge node 1110shown in FIG. 12 via the core nodes 1105 and 1109.

In the reception section of the edge node 1110, the frame separationsection 1509 establishes bit synchronization, byte synchronization andframe synchronization by use of the headers of the layer 1 frames.

After the establishment of the frame synchronization, the frameseparation section 1509 refers to the “Protocol” identifier of the layer1 frame and thereby judges whether or not the layer 1 frame is an ATMlayer 1 frame.

The frame separation section 1509 also refers to the “Packet Length”identifier of the layer 1 frame header and thereby grasps the totallength and the rear end of the layer 1 frame payload. In the case wherethe layer 1 frame is an ATM layer 1 frame, the frame separation section1509 sends the ATM layer 1 frame to the frame termination section 1507.

The frame termination section 1508 extracts an ATM layer 2 frame fromthe ATM layer 1 frame, extracts ATM cells from the ATM layer 2 frame,and sends the ATM cells to the ATM cell transmission section 1504. TheATM cells are transferred by the ATM cell transmission section 1504 tothe ATM device 1112 (1501).

As explained above, the ATM cells can be transferred together with dataof different protocols (STM signals, IP packets) by use of a commonframe format, therefore, different types of data can be handled andtransferred in a network concurrently and with a common method.

Therefore, the STM networks, the ATM networks and the IP networks whichhave been constructed separately and independently can be integrated orconstructed as a common integrated network.

Next, the transfer of IP packets in the data transfer system of FIG. 12will be explained in detail.

Referring to FIG. 15, in the transmission section of the edge node 1103,the IP packet reception section 1403 receives IP packets (IP packetdata) from the IP router 1102 (1400). The IP packet reception section1403 terminates the layer 1 and the layer 2 which are used between theIP router 1102 (1400) and the edge node 1103, thereby extracts IPpackets, and stores the IP packets in the IP layer 2 frame generationsection 1408.

The route label generation section 1406 generates a route label based onthe IP layer information (destination IP address, source IP address,“Protocol Identification”) contained in the IP packet header. Dependingon cases, header information of upper protocols (TCP (Transport ControlProtocol), UDP (User Datagram Protocol)) at the front end of the IPpacket payload is referred to for the generation of the route label.

The route label generation section 1406 sends the generated route labelto the IP layer 2 frame generation section 1408.

The flow label generation section 1407 generates a flow label based onthe header information of the IP packet. The flow label is a field whichis referred to in the network for conducting flow distribution to two ormore OCHs which are forming a link.

The flow labels have to be provided to the IP layer 2 frames so that thesame IP flows (that is, IP flows having the same destination IP addressand the same source IP address, or IP flows having the same destinationIP address and the same source IP address and the same parameter in theIP header information) will have the same flow labels.

The flow label is calculated uniquely from the IP header informationetc, however, it is preferable that the flow labels take random (asrandom as possible) values that are determined depending on the IPheader information. For example, the flow label can be calculated by theflow label generation section 1407 by conducting the Hash operation tothe IP layer information (the IP packet header). The flow labelgeneration section 1407 sends the generated flow label to the IP layer 2frame generation section 1408.

The IP layer 2 frame generation section 1408 generates an IP layer 2frame by packing the IP packet in the IP layer 2 frame payload and packsthe route label and the flow label in the IP layer 2 frame header. TheIP layer 2 frames generated by the IP layer 2 frame generation section1408 are stored in the IP layer 1 frame generation section 1412.

The scheduler section 1413 instructs the IP layer 1 frame generationsection 1412 to output an IP layer 1 frame to the frame multiplexingsection 1414 if the IP layer 1 frame generation section 1412 is storingan IP layer 1 frame. The scheduler section 1413 gives the aboveinstruction after instructing the ATM layer 1 frame generation section1409 to output an ATM layer 1 frame to the frame multiplexing section1414. According to the instructions of the scheduler section 1413, theIP layer 1 frame generation section 1412 outputs a primary IP layer 1frame to the frame multiplexing section 1414, giving higher prioritythan best effort IP layer 1 frames.

As mentioned before, a best effort IP layer 1 frame has to betransferred in a remaining space (best effort IP transfer space) betweenthe STM layer 1 frame, the ATM layer 1 frames and the primary IP layer 1frames in the 125 μsec transfer space, as shown in FIGS. 10 and 11.

Therefore, when the scheduler section 1413 instructs the IP layer 1frame generation section 1412 to output a best effort IP layer 1 frame,the scheduler section 1413 informs the IP layer 1 frame generationsection 1412 about the best effort IP transfer space length L (byte).

Based on the best effort IP transfer space length L, the IP layer 1frame generation section 1412 determines the length etc. of a besteffort IP layer 1 frame to be outputted to the frame multiplexingsection 1414, as shown in the flow chart of FIG. 21. Incidentally, inFIG. 21, the explanation is given ignoring the “Payload CRC” field, forthe sake of simplicity. In the case where the “Payload CRC” field isemployed, the “Payload CRC” field is added to each IP layer 1 frame whenthe IP layer 1 frame is generated and transferred as a single frame, aBOM frame, a COM frame or an EOM frame, and the length of the “PayloadCRC” field is taken into consideration in the calculations in the flowchart of FIG. 21.

When the IP layer 1 frame generation section 1412 received theinstruction (to output a best effort IP layer 1 frame to the framemultiplexing section 1414) and a length parameter (indicating the besteffort IP transfer space length L), the IP layer 1 frame generationsection 1412 first judges whether or not there is an EOM frame remainingtherein (step S2200). If a remaining EOM frame exists (“Yes” in the stepS2200), the IP layer 1 frame generation section 1412 compares the lengthM of the EOM frame with the best effort IP transfer space length L (stepS2201).

If the EOM frame length M is longer than the best effort IP transferspace length L (“M>L” in the step S2201), the IP layer 1 framegeneration section 1412 partitions the EOM frame and extracts the firstsegment of the EOM frame. The length of the extracted first segment(including a header) is set to L.

The IP layer 1 frame generation section 1412 outputs the extracted firstsegment of the EOM frame to the frame multiplexing section 1414 as a COMframe. The remaining segment of the EOM frame is stored in the IP layer1 frame generation section 1412 as an EOM frame (having a layer 1 frameheader) (step S2202), thereby the process is ended.

If the EOM frame length M is equal to the best effort IP transfer spacelength L (“M=L” in the step S2201), the IP layer 1 frame generationsection 1412 outputs the EOM frame to the frame multiplexing section1414 without partitioning the EOM frame (step S2203), thereby theprocess is ended.

If the EOM frame length M is shorter than the best effort IP transferspace length L (“M<L” in the step S2201), the IP layer 1 framegeneration section 1412 compares the best effort IP transfer spacelength L with the EOM frame length M and the minimal dummy frame lengthD added together (M+D) (step S2204).

If the length M+D is equal to the best effort IP transfer space length L(“M+D=L” in the step S2204), the IP layer 1 frame generation section1412 outputs the EOM frame (length: M bytes) to the frame multiplexingsection 1414 (step S2207) and thereafter outputs the minimal dummy frame(length: D bytes) to the frame multiplexing section 1414 (step S2208),thereby the process is ended.

If the length M+D is longer than the best effort IP transfer spacelength L (“M+D>L” in the step S2204), the IP layer 1 frame generationsection 1412 inserts the stuff data after the payload of the EOM frame.The length of the stuff data is set to L−M−1 bytes. The 1 byte is usedfor the “Stuffing Length” identifier which indicates the length of thestuff data. Therefore, in the EOM frame to be transmitted, the “StuffingLength” identifier (1 byte) is inserted at the top of the layer 1 framepayload and the stuff data (L−M−1 bytes) is inserted at the bottom ofthe layer 1 frame payload as shown in FIG. 7 (step S2205). Thereafter,the IP layer 1 frame generation section 1412 outputs the EOM frame tothe frame multiplexing section 1414 (step S2206), thereby the process isended.

If the length M+D is shorter than the best effort IP transfer spacelength L (“M+D<L” in the step S2204), the IP layer 1 frame generationsection 1412 outputs the EOM frame to the frame multiplexing section1414 and updates the value of the parameter L (best effort IP transferspace length L) into L−M (L−M→L) (step S2209).

If no remaining EOM frame exists (“No” in the step S2200) or if theupdate of the best effort IP transfer space length L has been conducted(step S2209), the IP layer 1 frame generation section 1412 judgeswhether a best effort IP layer 1 frame to be transferred next exists ornot (step S2210).

If no best effort IP layer 1 frame to be transmitted next exists (“No”in the step S2210), the IP layer 1 frame generation section 1412 outputsa dummy frame of the length L to the frame multiplexing section 1414 soas to implement the periodical transmission of the STM layer 1 frames(step S2211), thereby the process is ended.

If a best effort IP layer 1 frame to be transmitted next exists (“Yes”in the step S2210), the IP layer 1 frame generation section 1412 obtainsthe length B of the best effort IP layer 1 frame to be transmitted next(step S2212), and compares the best effort IP layer 1 frame length Bwith the best effort IP transfer space length L (step S2213).

If the best effort IP layer 1 frame length B is longer than the besteffort IP transfer space length L (“B>L” in the step S2213), the IPlayer 1 frame generation section 1412 partitions the best effort IPlayer 1 frame into a BOM frame of the length L and an EOM frame (stepS2214). Thereafter, the IP layer 1 frame generation section 1412 outputsthe BOM frame of the length L to the frame multiplexing section 1414 andstores the EOM frame (step S2215), thereby the process is ended.

If the best effort IP layer 1 frame length B is equal to the best effortIP transfer space length L (“B=L” in the step S2213), the IP layer 1frame generation section 1412 outputs the best effort IP layer 1 frameto the frame multiplexing section 1414 as a single frame, withoutpartitioning the best effort IP layer 1 frame (step S2216), thereby theprocess is ended.

If the best effort IP layer 1 frame length B is shorter than the besteffort IP transfer space length L (“B<L” in the step S2213), the IPlayer 1 frame generation section 1412 compares the best effort IPtransfer space length L with the best effort IP layer 1 frame length Band the minimal dummy frame length D added together (B+D) (step S2217).

If the length B+D is equal to the best effort IP transfer space length L(“B+D=L” in the step S2217), the IP layer 1 frame generation section1412 outputs the best effort IP layer 1 frame (length: B) to the framemultiplexing section 1414 as a single frame (step S2219) and thereafteroutputs the minimal dummy frame (length: D) to the frame multiplexingsection 1414 (step S2220), thereby the process is ended.

If the length B+D is longer than the best effort IP transfer spacelength L (“B+D>L” in the step S2217), the IP layer 1 frame generationsection 1412 inserts the stuff data after the payload of the best effortIP layer 1 frame to be transmitted next. The length of the stuff data isset to L−B−1 bytes. The 1 byte is used for the “Stuffing Length”identifier which indicates the length of the stuff data. Therefore, inthe best effort IP layer 1 frame to be transmitted next, the “StuffingLength” identifier (1 byte) is inserted at the top of the layer 1 framepayload and the stuff data (L−B−1 bytes) is inserted at the bottom ofthe layer 1 frame payload as shown in FIG. 7 (step S2221). Thereafter,the IP layer 1 frame generation section 1412 outputs the best effort IPlayer 1 frame to the frame multiplexing section 1414 (step S2222),thereby the process is ended.

If the length B+D is shorter than the best effort IP transfer spacelength L (“B+D<L” in the step S2217), the IP layer 1 frame generationsection 1412 outputs the best effort IP layer 1 frame to the framemultiplexing section 1414 as a single frame and updates the value of theparameter L (best effort IP transfer space length L) into L−B (L−B→L)(step S2218). Thereafter, the IP layer 1 frame generation section 1412returns to the step S2212.

By the algorithm which has been described above, the best effort IPtransfer space of the length L is precisely filled and thereby theperiodical transmission of the STM layer 1 frames (interval: 125 μsec)is implemented successfully.

The frame multiplexing section 1414 frame multiplexes the IP layer 1frames (the primary IP layer 1 frames and the best effort IP layer 1frames) from the IP layer 1 frame generation section 1412 with STM layer1 frames supplied from the STM layer 1 frame generation section 1410 andATM layer 1 frames supplied from the ATM layer 1 frame generationsection 1409, and transmits the frame-multiplexed layer 1 frames to thetransmission line (to the core node 1104).

In the reception section (1600, 1601) of the core node 1104, the layer 1termination section 1700 receives the frame-multiplexed layer 1 framesand establishes byte synchronization and frame synchronization withregard to each input line by checking the “Header CRC16” identifier ofeach layer 1 frame header.

The layer 1 termination section 1700 refers to the “Protocol”identifiers of the headers of the layer 1 frames, thereby extracts IPlayer 1 frames, and sends the IP layer 1 frames to the IP layer 2termination section 1703.

The IP layer 2 termination section 1703 extracts an IP layer 2 framefrom the payload of the IP layer 1 frame supplied from the layer 1termination section 1700 if the IP layer 1 frame is a single frame.

If the IP layer 1 frame supplied from the layer 1 termination section1700 is a BOM frame, the IP layer 2 termination section 1703 waits forthe arrival of COM frames and an EOM frame, and thereafter reconstructsan IP layer 2 frame by connecting the payloads of the BOM frame, the COMframes and the EOM frame.

If the stuff data has been contained in the IP layer 1 frame, the IPlayer 2 termination section 1703 removes the stuff data from the IPlayer 1 frame.

The priority processing scheduler 1705, after giving the instructions tothe STM layer 2 termination section 1701 and the ATM layer 2 terminationsection 1702, instructs the IP layer 2 termination section 1703 tooutput one or more primary IP layer 2 frames stored therein to the framemultiplexing section 1704. Thereafter, the priority processing scheduler1705 instructs the IP layer 2 termination section 1703 to output one ormore best effort IP layer 2 frames stored therein to the framemultiplexing section 1704.

According to the instructions of the priority processing scheduler 1705,the IP layer 2 termination section 1703 outputs the primary IP layer 2frames and the best effort IP layer 2 frames to the frame multiplexingsection 1704.

The frame multiplexing section 1704 frame multiplexes the IP layer 2frames (the primary IP layer 2 frames and the best effort IP layer 2frames) with STM layer 2 frames supplied from the STM layer 2termination section 1701 and ATM layer 2 frames supplied from the ATMlayer 2 termination section 1702, and sends the frame-multiplexed layer2 frames to the layer 2 frame switch 1602 of the core node 1104.

The layer 2 frame switch 1602 transmits the layer 2 frames toappropriate output lines (transmission section 1603 or 1604) based onthe label information contained in the layer 2 frame headers.

In the transmission section (1603, 1604) of the core node 1104, theframe separation section 1804 separates the frame-multiplexed layer 2frames depending on their protocols (based on the control informationtransferred in the core node 1104), extracts IP layer 2 frames, andsends the IP layer 2 frames to the IP layer 1 frame generation section1803.

According to the instructions of the transmission scheduler 1805, the IPlayer 1 frame generation section 1803 converts the IP layer 2 framesinto IP layer 1 frames and outputs the IP layer 1 frames to the framemultiplexing section 1800. The conversion from the IP layer 2 framesinto the IP layer 1 frames is conducted in the same way as theconversion which is conducted in the edge node 1103.

The frame multiplexing section 1800 frame multiplexes the IP layer 1frames from the IP layer 1 frame generation section 1803 with STM layer1 frames supplied from the STM layer 1 frame generation section 1801 andATM layer 1 frames supplied from the ATM layer 1 frame generationsection 1802, and transmits the frame-multiplexed layer 1 frames to atransmission line (to the core node 1105).

FIGS. 13 and 14 are schematic diagrams showing the transfer of the IPlayer 1 frames in a network by use of the route label and the flowlabel.

The route label which is contained in the layer 2 frame header of an IPlayer 1 frame is used for determining relaying nodes (core nodes) fortransferring the layer 1 frame. In the example of FIG. 13, the IP layer1 frame is transferred from an edge node (EN) 1200 to an edge node (EN)1207 via core nodes (CN) 1201, 1202 and 1204. The core node (CN) 1201refers to the route label contained in the IP layer 1 frame and outputsthe IP layer 1 frame to an output line (output port) corresponding tothe route label, thereby the IP layer 1 frame is transferred to the corenode (CN) 1202. Thereafter, switching is executed similarly by the corenodes (CN) 1202 and 1204, and thereby the IP layer 1 frame istransferred to the edge node (EN) 1207.

Each link between two core nodes is composed of two or more wavelengths(optical channels), however, the route label does not designate thewavelength for being used. The route label is only used for thedetermination of the transfer route of the IP layer 1 frame (thesequence of relaying nodes).

The flow label which is contained in the layer 2 frame header of an IPlayer 1 frame designates a wavelength to be used for transferring the IPlayer 1 frame when a link is composed of two or more wavelengths. Thewavelength to be used for transferring an IP layer 1 frame is determinedby each core node (CN) for each IP layer 2 frame (for each IP layer 1frame), by referring to the flow label contained in the IP layer 1 frameas shown in FIG. 14. In the case of FIG. 14, the core node (CN) 1301selects a wavelength from two or more wavelengths forming the linkbetween the core nodes (CN) 1301 and 1302 by referring to the flow labelof the IP layer 1 frame, and transmits the IP layer 1 frame to the corenode (CN) 1302 by use of the selected wavelength. Incidentally, in acore node (CN), IP layer 2 frames having the same flow labels aretransmitted by use of the same wavelength.

Referring again to the data transfer system of FIG. 12, in the receptionsection of the edge node 1110, the frame separation section 1509receives frame-multiplexed layer 1 frames and establishes bitsynchronization, byte synchronization and frame synchronization byreferring to the layer 1 frame headers.

The frame separation section 1509 refers to the “Protocol” identifiersof the layer 1 frame headers, thereby extracts IP layer 1 frames fromthe frame-multiplexed layer 1 frames, and sends the IP layer 1 frames tothe frame termination section 1506.

The frame termination section 1506 extracts an IP layer 2 frame from thepayload of the IP layer 1 frame supplied from the frame separationsection 1509 if the IP layer 1 frame is a single frame.

If the IP layer 1 frame supplied from the frame separation section 1509is a BOM frame, the frame termination section 1506 waits for the arrivalof COM frames and an EOM frame, and thereafter reconstructs an IP layer2 frame by connecting the payloads of the BOM frame, the COM frames andthe EOM frame.

If the stuff data has been contained in the IP layer 1 frame, the frametermination section 1506 removes the stuff data from the IP layer 1frame.

The frame termination section 1506 extracts an IP packet from the IPlayer 2 frame and sends the IP packet to the IP packet transmissionsection 1503. The IP packet transmission section 1503 transmits the IPpacket to the IP router 1113 (1500).

As described above, in the operation of the data transfer system inaccordance with the embodiment of the present invention, the STM layer 1frames are transferred at fixed periods (125 μsec). Bit synchronizationis established in the physical layer, and byte synchronization and framesynchronization are established by use of the “Header CRC16” identifier,thereby the STM signals are necessarily transferred at fixed intervals(125 μsec) maintaining the end-to-end circuit quality monitoringfunctions (end-to-end performance monitoring functions).

The STM signals, the ATM cells and the IP packets are transferred by useof a common frame format, therefore, the different types of informationcan be handled and managed in a network concurrently by a common method.

Therefore, the STM networks, the ATM networks and the IP networks whichhave been constructed separately and independently can be integrated orconstructed as a common or integrated network.

By the definition of the route label and the flow label as transferinformation for the IP layer 2 frames, IP packets can be transferredappropriately by simple procedures even when each link is composed oftwo or more wavelengths by means of WDM (Wavelength DivisionMultiplexing).

When the above embodiment is applied to an IP network (without STM andATM), the primary IP layer 1 frames can be transferred at fixedintervals (125 μl sec, for example), and thereby the transfer of theprimary IP layer 1 frames can be conducted with the same high quality(without delay variation) as the STM layer 1 frames of the aboveembodiment.

As set forth hereinabove, by the frame construction method, the frameconstruction device and the data transfer system in accordance with thepresent invention, different types of data (STM signals, ATM cells andIP packets) can be transferred in a network by use of a common frameformat.

The layer 1 frames, containing the STM signals, the ATM cells and the IPpackets addressed to different destinations, can be transferred to theirdestinations appropriately.

STM networks, ATM networks and IP networks which have been constructedseparately and independently can be integrated or constructed as acommon or integrated network.

Bit errors which can occur during the transfer of the layer 1 frames canbe detected by each node by use of the “Payload CRC” field, thereby thelink monitoring can be executed by each node. By use of the OAM frames,path monitoring with regard to a path from the ingress point to theegress point can be conducted by a node at the egress point by referenceto the OAM frame.

The layer 2 frames and the layer 1 frames in accordance with the presentinvention can be constructed regardless of the size of the STM signal,the ATM cell or the IP packet which is packed in the layer 2 framepayload. Therefore, the layer 1 frame is constructed even if the size ofdata (STM signal, ATM cell or IP packet) to be transferred is verysmall. On the other hand, even when the amount of best effort IP packetsto be transferred is very large, by the priority processing of the aboveembodiment in order of STM, ATM, primary IP and best effort IP, the STMlayer 1 frames and the ATM layer 1 frames (and the primary IP layer 1frames) can be transferred without being affected by the congestion inthe best effort IP traffic.

The layer 1 frames in accordance with the present invention are framemultiplexed and transferred with predetermined periodicity (125 μsec,for example), thereby the bit synchronization in the physical layer canbe established. By use of the “Header CRC16” identifiers of the layer 1frame headers, the byte synchronization and the frame synchronizationare established.

The type of data which is contained and transferred in the layer 1 framecan be detected by the reference to the “Protocol” identifier of thelayer 1 frame header.

The priority (in data transfer) of the data contained and transferred inthe layer 1 frame can be detected by the reference to the “Priority”identifier of the layer 1 frame header, thereby the STM layer 1 frames(CBR traffic) are transferred with the highest priority.

The length of the layer 1 frame header is fixed (6 bytes in theembodiment), thereby the reference to the header information(identifiers) can be conducted by each node easily and correctly.

In the case where the stuff data has been stuffed in the layer 1 framepayload in order to adjust the length of the layer 1 frame in the frametransfer, a node which received the layer 1 frame can easily remove thestuff data by the reference to the “Stuff” identifier and the “StuffingLength” identifier.

The layer 1 frame in accordance with the present invention canaccommodate and transfer the N-channel trunk signal of N×64 Kbps whichhas been transferred between conventional switches, therefore, theconventional telephone networks (voice transmission telecommunicationnetworks) can be accommodated in the data transfer system of the presentinvention.

The STM layer 1 frames of the present invention can be transferred atprecisely fixed intervals (125 μsec in the above embodiment) by theadjustment of the length of the best effort IP layer 1 frame. Theadjustment of the best effort IP layer 1 frame length is conducted bythe partitioning of the best effort IP layer 1 frame, the insertion ofthe stuff data etc. as explained referring to FIG. 21. Even when thereis no best effort IP layer 1 frame to be transferred, the periodicaltransfer of the STM layer 1 frames (125 μsec) is maintained by thetransfer of the dummy frames.

In the above embodiment, the transfer of the STM signals (contained inthe STM layer 1 frames) can be executed with higher priority than theATM signals (contained in the ATM layer 1 frames) and the IP packets(contained in the IP layer 1 frames), and the transfer of the ATMsignals can be conducted with higher priority than the IP packets.

When the present invention is applied to an IP network (without STM andATM), the primary IP layer 1 frames can be transferred at fixedintervals (125 μsec, for example), thereby the transfer of the primaryIP packets can be conducted with the same high quality (without delayvariation) as the conventional STM signals.

The best effort IP packets, which is of lower priority in the IPpackets, are transferred with the lowest priority in the embodiment,thereby the STM signals, the ATM cells and the primary IP packets, whichshould be handled as high priority traffic, can be transferred withhigher priority.

A core node which relays the layer 1 frames can judge the type(protocol) of data which is contained in the layer 1 frame by thereference to the “Protocol” identifier of the layer 1 frame header,thereby the core node is enabled to judge the priority of transfer ofthe layer 1 frame.

The core node which relays the layer 1 frames can transfer the STMsignals (STM layer 1 frames) with the highest priority among the varioustypes of data at precisely fixed intervals (125 μsec) so as to implementthe end-to-end performance monitoring functions.

The core node which relays the layer 1 frames can determine the nextnode (output port) for transferring the layer 1 frame by the referenceto the route label of the layer 2 frame header.

The core node which relays the layer 1 frames can select the wavelengthfor the transfer of the layer 1 frame by the reference to the flow labelof the layer 2 frame header.

Incidentally, while the processes of the flow chart of FIG. 21 for thetransfer of the best effort IP layer 1 frames were explained asprocesses on the level of layer 1 frames, it is also possible to let theedge nodes and core nodes conduct equivalent processes (partitioning,stuffing, etc.) on the level of layer 2 frames or IP packets.

The priority processing which was employed in the above embodiment isonly an example and other algorithms can also be employed for thepriority processing. For instance, while the transfer of a primary IPlayer 1 frame in the fixed cycle (125 μsec) was executed after thetransfer of all the ATM layer 1 frames stored in the node in the aboveembodiment, the transfer of the primary IP layer 1 frame can also beexecuted after the transfer of one ATM layer 1 frame. In the same way,while the transfer of a best effort IP layer 1 frame in the fixed cycle(125 μsec) was started after the transfer of all the primary IP layer 1frames stored in the node, the transfer of the best effort IP layer 1frame can also be started after the transfer of one primary IP layer 1frame. The length of the fixed cycle (125 μsec) employed in the aboveembodiment can be changed depending on design requirements of the datatransfer system.

While the present invention has been described with reference to theparticular illustrative embodiments, it is not to be restricted by thoseembodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can change or modify the embodimentswithout departing from the scope and spirit of the present invention.

1. A method of generating a plurality of layer 1 frames, having a commonframe format, from a plurality of types of layer 2 data, includingSynchronous Transfer Mode (STM) signals, Asynchronous Transfer Mode(ATM) cells, primary Internet Protocol (IP) packets, and best effort IPpackets, the method comprising: forming a payload for a layer 1 framethat includes the data of a layer 2 frame; forming, based on a type ofthe data of the layer 2 frame, a layer 1 frame header including: apacket length field to indicate a size of a payload portion of the layer1 frame, a priority field to indicate a priority of the layer 1 frame, aprotocol field to identify a protocol of the payload based on the typeof the data in the layer 2 frame, a frame mode field to indicate acorrespondence between the layer 1 frame and the layer 2 frame includedwithin the payload, a stuff field to indicate whether stuff data iscontained in the layer 1 frame, and a cyclic redundancy check (CRC)field to indicate a CRC result; and outputting the layer 1 frames in thecommon frame format, where the layer 1 frames that include the STM layer2 data are periodically output, and when an idle transfer spaceimmediately precedes a particular layer 1 frame that includes the STMlayer 2 data being output: inserting a dummy frame into the idletransfer space when the idle transfer space is sufficient to accommodateat least a minimum-length dummy frame, and inserting, when the idletransfer space is not sufficient to accommodate the minimum-length dummyframe, a partitioned layer 1 frame that includes the best effort IPpackets or a layer 1 frame that includes the best effort IP packets andthe stuff data into the idle transfer space, where a length of the stuffdata is smaller than a sum of a length of the layer 1 frame header andthe CRC field.
 2. The method of claim 1, where the layer 2 frameincludes a layer 2 header and a layer 2 payload section, and where thelayer 2 header is located at the beginning of the payload of the layer 1frame.
 3. The method of claim 1, further comprising: partitioning thelayer 2 frame into segments; and including different ones of thesegments in different layer 1 frames.
 4. The method of claim 1, wherethe payload for the layer 1 frame is included in a variable-lengthfield.
 5. The method of claim 4, where a length of the variable-lengthfield is set between zero Kbytes and 64 Kbytes.
 6. The method of claim1, where the packet length field begins the layer 1 frame header, thepriority field follows the packet length field, the protocol fieldfollows the priority field, the frame mode field follows the protocolfield, the stuff field follows the frame mode field, and the CRC fieldfollows the stuff field.
 7. The method of claim 6, where the layer 1frame header consists of six bytes of information.
 8. The method ofclaim 1, where the layer 1 frame header consists of six bytes ofinformation.
 9. The method of claim 1, further comprising: forming thepacket length field as two bytes of information; forming the priorityfield as 10 bits of information; forming the protocol field as threebits of information; forming the frame mode field as two bits ofinformation; forming the stuff field as one bit of information; andforming the CRC field as two bytes of information.
 10. A network devicecomprising: means for receiving one or more of an ATM (AsynchronousTransfer Mode) cell, a primary Internet Protocol (IP) packet, a bestefforts IP packet, or an STM (Synchronous Transfer Mode) signal fromanother network device; means for forming a layer 1 frame that includesthe received ATM cell, primary IP packet, best efforts IP packet, or STMsignal as payload data within the layer 1 frame; means for forming aheader for the layer 1 frame, the header including: a packet lengthfield to indicate a size of the payload data of the layer 1 frame, apriority field to indicate a priority of the layer 1 frame, a protocolfield to identify a protocol of the payload data, a frame mode field toindicate a correspondence between the layer 1 frame and the payload datawithin the layer 1 frame, a stuff field to indicate whether stuff datais contained in the layer 1 frame, and a cyclic redundancy check (CRC)field to indicate a CRC result; means for determining whether the layer1 frame has payload data associated with an STM protocol or the layer 1frame is to be transferred via a transfer space before another layer 1frame having payload data associated with the STM protocol; means forinserting, when it is determined that the layer 1 frame is to betransferred via the transfer space before the other layer 1 frame havingpayload data associated with the STM protocol: a dummy frame into anidle transfer space between the transfer space and the other layer 1frame having payload data associated with the STM protocol, when theidle transfer space is sufficient to accommodate at least aminimum-length dummy frame, and a partitioned layer 1 frame thatincludes payload data not associated with the STM protocol or a layer 1frame that includes payload data not associated with the STM protocoland the stuff data into the idle transfer space, when the idle transferspace is not sufficient to accommodate the minimum-length dummy frame;and means for transferring the layer 1 frame in a common frame formatirrespective of the payload data to maintain frame synchronization. 11.The network device of claim 10, where the network device is an edgerouter.
 12. The network device of claim 10, where the packet lengthfield begins the layer 1 frame header, the priority field follows thepacket length field, the protocol field follows the priority field, theframe mode field follows the protocol field, the stuff field follows theframe mode field, and the CRC field follows the stuff field.
 13. Thenetwork device of claim 12, where the layer 1 header consists of sixbytes of information.
 14. The network device of claim 10, where the CRCresult is calculated based on the packet length field, the priorityfield, the protocol field, the frame mode field, and the stuff field.15. The network device of claim 10, where the payload for the layer 1frame is included in a variable-length field.
 16. The network device ofclaim 10, where the layer 1 frame header consists of six bytes ofinformation.
 17. A method of transferring, in a common layer 1 frameformat, a plurality of types of data, including Synchronous TransferMode (STM) signals, Asynchronous Transfer Mode (ATM) cells, primaryInternet Protocol (IP) packets, and best effort IP packets, the methodcomprising: forming a payload for the layer 1 frame that includes dataof a layer 2 frame; forming a layer 1 frame header including: a packetlength field to indicate a size of a payload portion of the layer 1frame, a priority field to indicate a priority of the layer 1 frame, aprotocol field to identify a protocol of the data in the layer 2 frame,a frame mode field to indicate a correspondence between the layer 1frame and the layer 2 frame included within the payload, a stuff fieldto indicate whether stuff data is contained in the layer 1 frame, and acyclic redundancy check (CRC) field to indicate a CRC result; andoutputting the layer 1 frame in the common frame layer 1 format, wheretwo or more of the layer 1 frames that include the STM layer 2 data aretransferred at fixed intervals, and when an idle transfer space isdisposed between the fixed intervals: inserting a dummy frame into theidle transfer space when the idle transfer space is sufficient toaccommodate at least a minimum-length dummy frame, and inserting, whenthe idle transfer space is not sufficient to accommodate theminimum-length dummy frame, a partitioned layer 1 frame that includes atype of layer 2 data other than the STM layer 2 data or a layer 1 framethat includes a type of layer 2 data other than the STM layer 2 data andthe stuff data into the idle transfer space.
 18. The method of claim 17,further comprising: forming the packet length field as two bytes ofinformation; forming the priority field as 10 bits of information;forming the protocol field as three bits of information; forming theframe mode field as two bits of information; forming the stuff field asone bit of information; and forming the CRC field as two bytes ofinformation.